This inscription is most readily comparable to the addendum at Behistun:

(71a) King Darius says: The following is what I did in the second and third year of my rule. The province called Elam revolted from me. An Elamite named Atamaita they made their leader. Then I sent an army unto Elam. A Persian named Gobryas, my servant, I made their leader. Then Gobryas set forth with the army; he delivered battle against the Elamites.

(71a) Then Gobryas destroyed many of the host and that Atamaita, their leader, he captured, and he brought him unto me, and I killed him. Then the province became mine.

(72) King Darius says: Those Elamites were faithless [more literally, hostile] and Ahuramazda was not worshipped by them. I worshipped Ahuramazda; by the grace of Ahuramazda I did unto them according to my will.

(73) King Darius says: Whoso shall worship Ahuramazda, divine blessing will be upon him, both while living and when dead.

(74a) King Darius says: Afterwards with an army I went off to Scythia, after the Scythians who wear the pointed cap. These Scythians went from me. When I arrived at the river, I crossed beyond it then with all my army. Afterwards, I smote the Scythians exceedingly; [one of their leaders] I took captive; he was led bound to me, and I killed him.

(74b) [Another] chief of them, by name Skunkha, they seized and led to me. Then I made another their chief, as was my desire. Then the province became mine.

(75) King Darius says: Those Scythians were faithless and Ahuramazda was not worshipped by them. I worshipped Ahuramazda; by the grace of Ahuramazda I did unto them according to my will.

(76) King Darius says: [Whoso shall worship] Ahuramazda, [divine blessing will be upon him, both while] living and [when dead.]

Comparing Dareios and Xerxes to Cyrus is difficult, because of the limited material and poor understanding of Cyrus we have, and because of the discontinuity between the Teispid and Achaemenid dynasties. See these two mini-essays of mine for more context:

• The Cyrus Cylinder - myth, fact and forgery

• The Behistun Inscription and the Conspiracy that made Darius king

Before we can discuss religion usefully, we need to think about the ethno-cultural context of "Persia" for a moment. The urbanized region east of the Tigris, Elam, long predates the arrival of Persians. Elamite was the administrative language of that heartland throughout most of the Empire's lifespan (only a single tablet in Old Persian is known from the Persepolis archives). Toward the end of the 7th century, the great Assyrian monarch Ashurbanipal sacked the hell out of Elam. It is probably after this Tishpa (or Teispes), the ancestor Cyrus traces his house back to, comes to power. It is notable that Tishpa, Kanbujiya (Cambyses), and Kurush/Kurash (Cyrus) are in all likelyhood Elamite names; on the other hand, the names of three of Cyrus' children (Atosa, Artastuna, Bardiya) are Persian. Cyrus' family may therefore have been a Persian dynasty that assumed Elamite names, if we consider the distinction between Persian and Elamite useful to make.

Cyrus never calls himself King of Persia, but always uses King of Anshan. He names Ashurbanipal as a predecessor in the Cyrus cylinder, and there is nothing obviously Persian, or even Elamite, that we can discern about anything attested about him apart from his name and place of origin. Most likely, he was a follower of the Elamite religion, a polytheist religion centered around the worship of Khumban, a sky god.

Dareios, however, makes his Persian cultural identity very obvious, and makes Zoroastrianism an essential aspect of the royal cult. Now, we should understand this Zoroastrianism with some nuance - Greek sources, as well as figures, suggest that Ahuramazda (whom the Greeks identified with Zeus) was largely conflated with Khumban. None of the Achaemenid kings were hesitant to adopt the trappings of local cults of royalty to retain their power, but naturally, the support of Iranian nobility was more important than anything else. His inscriptions are therefore heavily laced with Zoroastrian concepts of Truth, Lies, and so on. His very name, Daraya-Wahush, meaning _One who does [moral] good, oozes of Zoroastrianism.

Now, there is really nothing that suggests that Cyrus' religious policy differed markedly from that of Dareios. What we do know with reasonable certainty is that Dareios was a usurper, a highly effective propagandist, and a reformer, whose tax reforms allowed him to undertake massive construction projects and create the long-lasting royal cult of the dynasty. That's where we can begin to contextualize his assertions of a lack of Mazda-worship among Elamites and Scythians - such assertions were integral to his claim to divine authority in subjugating them.

And that's also where we should place Xerxes' Daiva inscription. While we don't know if it was an actual event or more a general ideological statement (I favour the latter), Xerxes' claim to have suppressed Daiva-worshippers mesh well with Dareios' general assertions of favouring Truth over Lies and putting down "hostile" forces that did not worship Ahuramazda. The Mantra of being "blessed in life and death" that follows both underscores the similarity. This doesn't mean that they enforced Mazda-worship over the entire Middle East and Central Asia - the very suggestion would probably have struck them as absurd. On the other hand, they would possibly have had limited toleration for straying outside the bounds of acceptable practice (e.g. purity rites) by Mazda-worshippers.

So, were Xerxes' and Dareios' conceptions of their rulership fundamentally different from that of Cyrus? Probably, yes. Did they abolish some previous policy of religious tolerance? No.