It's difficult to answer to such a broad question, so let's analysis point by point Hitler's competence.

Strategic/Political level: He won a bunch of significative success in the pre war, managing to remilitarize the Rhine (forbidden by the treaty of Versailles), annex Austria, Czechoslovakia and the city of Memel from Lithuania, essentially by intimidating the western democracy and leading an ultra aggressive policy. However after 1939, things changed. He declared war on Poland and did not expect a western intervention, his initial plan was to start a global war in 1944-1945... He never built a comprehensive and coherent overall strategy and solely rely on an ultra aggressive behaviour. Exemple: he expected the British to seek a peace after the battle of France... But Churchill refused and thus Hitler decided to start the battle of Britain. After the failure to destroy the RAF, he then turned to the east, persuaded that defeating the USSR would force the British to sign peace (it is not the only reason for the eastern front but it is one among them). It's basically a perpetual spiral of violence with even more aggressive solution each time he failed to reach his goal; he managed to get some success against weak opponents but things changed when he got a determined coalition instead. Also noticed that he strictly had no reason to declare war on the US after Pearl Harbour... (Roosevelt was not sure to have enough support from the congress to declare war on Germany, so he only targeted Japan in his "day of infamy" speech. Hitler allowed him to bypass this problem!)

Operational and tactical level

Bad. In 1940, Manstein designed a plan with a clear operational focus, the famous sickle cut in the Ardennes to separate the Allied nations forces in two. But Barbarossa has no focus, the objective is Leningrad in July 1941, Kiev in August and Moscow in September. As a result, the German army ended overextended, with way too long supply lines and a material used by attrition without managing to beat the USSR... Which obviously put the Wehrmacht in a terrible position against Soviet winter counterstrikes.

Again in 1942, [Fall Blau] (https://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Eastern_Front_1942-05_to_1942-11.png/800px-Eastern_Front_1942-05_to_1942-11.png) had no operative priority which made it fail. After the battle of Rostov he thought that he won the campaign and thus divided his army group south in 2, one aiming the city of Stalingrad and one the Caucasus (which he will personally led with very mediocre results). Both of his army would fail to reach their goal. The irony is that Stalingrad is initially defenseless, having almost no soviet soldier there but german 6th army had not enough oil to push until the city, because the supply went to the other half army group. When finally the 6th army can advance, it is too late, it will have to fight one of the (if not THE) toughest battle of the war...

Also, Hitler can't support any withdraw. Very arguably, by sacking generals who retreated in winter 1941 he prevented a general disastrous retreat (it is a quite contested thing, won't extend here). But later this would lead to many disasters. One example: By late 1942, north Africa is lost, the British under Montgomery are slowly but surely repelling Rommel in Egypt and Libya while the Americans had landed in Morocco (Operation Torch). What's Hitler decision? Sending over 100 000 reinforcements who will be later captured in the battle of Tunisia and would latter lack for the defense of Italy and France... Not only Hitler refuse operational or strategic withdraw (to have a better line of defense, to shorten the front to gain some troop in reserves etc...) but even at a tactical level which is completely absurd. In 1944, before the summer great offensive, Vitebsk is already 3/4 surrounded by the soviet and impossible to defend, still Hitler refuse to evacuate the city. Again it will end in a disaster, the worst one of the whole german history, the soviet ["Operation Bagration"] (https://en.wikipedia.org/wiki/Operation_Bagration). Even for protecting the german soldiers from deadly artillery preparation from the soviet he would often refuse a very short withdraw...

One of the reason of his inept military leadership is that Hitler is too much obsessed with the high geostrategic level instead of the immediate one. This could be positive like in 1942, where he is the one that target the oil field of Maikop/Grozny/Bakou in the Caucasus (while the other commander of the army intended to destroy the Red Army in a "vernichtungsschlacht" at Moscow, an illusionary concept of decisive battle of annihilation, Hitler proved that he somewhat had a better understanding of the modern warfare) or catastrophic... He refused to evacuate Norway, leaving their between 200 and 300 000 men until the end of the war. The occupation of Norway allow the Reich to control the export of the swedish ores which are very important for the Reich economy. But the immediate survival of the Reich is obviously more important than the somehow distant consequences of the loss of Swedish iron and other metals.

Last but not least: the "Haltebefehl" order which halt the German Panzer armies just before Dunkirk and let the British Expeditionary Force flee instead of destroying it. Although Gerd Von Rundstedt is the one who suggested it, Hitler is the supreme commander and could have insist on pursuing the offensive.

Economic level

Terrible, the economy of Germany is archaic and feudal, corruption and intern rivalry are everywhere (One exemple: there is no coordination for the nuclear research, 7 different organisms are working on it, the Wilhelm Kaiser institute, the SS, the Armament office of the heer etc... )

Hitler is unable to totally mobilize the german economy until 1943, until this year there are 1 million domestic worker although Germany has been at war for 4 years! And it is not until spring 1944 that the production of ammunition exceed the one of 1918!!

He is also personally responsible of some disastrous intervention in the industry. The most famous is his demand to turn the Me 262, the first world jet powered aircraft into a fighter-bomber which would delay his development by several months...

PS: the Zimmermann telegram between Germany and Mexico took place in WW1, not Hitler fault :-).