The wikipedia says that Susa was the capital of Elam, written something like Elymais in the Greek texts. But Greco-Roman reports of the deaths of Antiochus iii and Antiochus iv seem to confuse these sites. Antiochus iii goes beyond Susa before being overwhelmed by the fierce tribes of the Elymains according to the Geographer Strabo. This seems odd since coming from Babylon he Susa would have been on the far side of Elam if it was still within Elam and beyond Elam if they were separate entities. Strabo does say, shortly on, that each person knows his own territory the best though.
At any rate Alymais must refer to a satrapy, not a city, so I would assume that most eras the capital would be Susa. But some writings suggest the two had become separate entities during the Seluecid rule somehow.
Are these ancinet Greek sources simply wrong? Is the Wikipedia page wrong?
I'm not entirely clear on the source of your confusion since neither Susa nor Elymais are mentioned on Antiochus IV's wiki page, but neiter Wikipedia page is very good in this case so I'll see if I can clear anything up.
Let's start with what Strabo has to say about Elymais
Neighbouring Susis is the part of Babylonia which was formerly called Sitacenê, but is now called Apolloniatis. Above both, on the north and towards the east, lie the countries of the Elymaei and the Paraetaceni, who are predatory peoples and rely on the ruggedness of their mountains. But the Paraetaceni are situated closer to the Apolloniatae, and therefore treat them worse. The Elymaei carry on war against both that people and the Susians, whereas the Uxii too carry on war against the Elymaei. - Strabo, Geography, 15.3.12
For Sitacenê too, both extensive and fertile, lies between Babylon and Susis, so that the whole of the journey for people travelling from Babylon to Susa is through Sitacenê towards the east; and the journey for people travelling from Susa into the interior of Persis through Uxia, and for people travelling from Persis into the middle of Carmania, is also towards the east. Now Carmania in encircled on the north by Persis, which is a large country; and bordering on this country are Paraetacenê and Cossaea as far as the Caspian Gates, which is inhabited by mountainous and predatory tribes. And bordering on Susis is Elymaïs, most of which is rugged and inhabited by brigands; and bordering Elymaïs are Media and the region of the Zagrus...There are three entrances into the country {Elymais} that have been supplied by nature: one from Media and the region of the Zagrus through Massabaticê; another from Susis through Gabianê (these, both Gabianê and Massabaticê, are provinces of Elymaea), and the third from Persis. - Strabo, Geography, 16.1.17-18
The first thing to note, if you're reading Strabo and trying to match things up on a map, is that "Sitacene" is actually northeast of Babylon. It does not refer to the region that is in between Babylon and Susis as the crow flies, but the area of northeastern Mesopotamia where it was easiest to enter and traverse the Zagros Mountains on the way to Susa. In antiquity, the marshes of southern Mesopotamia were difficult to traverse and a route going north, around the marshes, had been well established since the early Bronze Age.
Strabo is not talking about the city of Susa when he says "Susis," but the city and the surrounding region as an area distinct from the other regions being discussed. While Susa was the traditional capital of Elam, that was not the case 100% of the time and the exact use of different place names and ethnic names shifted around over the centuries. In this case "Elymais" does have its roots in the word "Elam," but it is referring to a specific segment of traditional Elamite territory: the mountains northeast of Susa around the Zard-Kuh subrange.
This is not at all unusual in Elamite history. Elam was divided into regional kingdoms or closer to a loose confederation at least as often as it was a strong kingdom. The mountain tribes of this same region were a source of unrest in the late Achaemenid Persian Empire as well. As Stabo understood the region, Susis and the surrounding plains were one region with an important political center, surrounded by mountainous regions with warring tribal groups.
As for the kings, here are all of the primary accounts of both Antiochus III's and Antiochus IV's deaths:
Antiochus III Megas
In Syria, meanwhile, king Antiochus, being burdened, after he was conquered by the Romans, with a heavy tribute under his articles of peace, and being impelled by want of money or stimulated by avarice, brought up his army one night, and made an assault upon the temple of Jupiter in Elymais, hoping that he might more excusably commit sacrilege under plea of wanting money to pay his tribute. But the affair becoming known, he was killed by a rising of the people who dwelt about the temple. - Justin Epitome of Pompeius Trogus 32.2
Antiochus, pressed for funds and hearing that the temple of Bel in Elymaïs had a large store of silver and gold, derived from the dedications, resolved to pillage it. He proceeded to Elymaïs and after accusing the inhabitants of initiating hostilities, pillaged the temple; but though he amassed much wealth he speedily received meet punishment from the gods - Diodorus Siculus Library of History 29.15
Now when Antiochus the Great attempted to rob the temple of Belus, the neighbouring barbarians, all by themselves, attacked and slew him. - Strabo, Geography, 16.1.18
Antiochus IV Epiphanes
He was terrified and withdrew from the country {Egypt}, and robbed the temple of Venus Elymais; then died of a wasting disease, leaving a son nine years of age, the Antiochus Eupator already mentioned. - Appian Syrian Wars 14.66
In Syria King Antiochus, wishing to provide himself with money, decided to make an expedition against the sanctuary of Artemis in Elymaïs. On reaching the spot he was foiled in his hopes, as the barbarian tribes who dwelt in the neighborhood would not permit the outrage, and on his retreat he died at Tabae in Persia, smitten with madness, as some people say, owing to certain manifestations of divine displeasure when he was attempting this outrage on the above sanctuary. - Polybius Histories 31.9
When the leader reached Persia with a force that seemed irresistible, they were cut to pieces in the temple of Nanea by a deception employed by the priests of the goddess Nanea. On the pretext of intending to marry her, Antiochus came to the place together with his Friends, to secure most of its treasures as a dowry. When the priests of the temple of Nanea had set out the treasures and Antiochus had come with a few men inside the wall of the sacred precinct, they closed the temple as soon as he entered it. Opening a secret door in the ceiling, they threw stones and struck down the leader and his men; they dismembered them and cut off their heads and threw them to the people outside. - 2 Maccabees 1:13-16
Additionally there is an account for Antiochus IV by Porphyry of Tyre that I do not have access to, which is usually described as agreeing with Appian and Polybius.
Right away it should be pretty clear that the two kings died in very similar circumstances. Both died soon after pillaging and Elymaean temple. Antiochus III was killed by Elymaeans. The three Greco-Roman sources describe Antiochus IV as dying of illness. 2 Maccabees is the outlier, placing Antiochus IV in Persia and attributing his death to the locals. Given the book's heavily mythologized narrative and a general tendency in classical literature to use "Persia" as a catchall for Iranian territory, the Maccabees narrative is typically taken as the least accurate.
Strabo and Justin both suggest that Elymais refused to submit and pay tribute to Antiochus III. There is nothing to suggest that this would have changed under Antiochus IV. Whether they thought of it as a rebellious province or a hostile neighbor, both kings saw no problem with raiding Elymaean territory as a quick cash grab. Nothing about that suggests that their stories were confused by the ancient authors. Raiding enemy territory was a common tactic in the ancient world, and temples were often extremely wealthy. Elamite history in particular has several examples of temples acting as the primary financial institution in any given area.
The deity of the temple actually helps establish that these sources are indeed referring to two separate events. Antiochus III is credited with raiding a temple of "Bel," a Mesopotamian storm god often equated with Jupiter and used as an epithet for the Babylonian chief-god Marduk. This could be an actual temple to a Mesopotamian Bel, or it could be a reference to the Zoroastrian God, Ahura Mazda who was often conflated with Bel in foreign sources. Both were worshiped in Elam at the time.
Antiochus IV is credited with raiding the temple of a goddess. This is almost certainly the Zoroastrian divinity Anahita, who was alternately identified with Venus/Aphrodite or Artemis depending on the context. Maccabees' use of Nanea is unique and could be a translation from Anahita or the Mesopotamian Nanaya who was likewise associated with Anahita in some local contexts.
The fact that the actual method of death (killed vs disease) and the temple in question (god vs goddess) are different establishes that these authors were writing about to distinct events. They just happen to be events concerning two very similar kings in very similar contexts within a few decades of each other.