@murph
Germany entered the war Europe's largest and most industrialized country (Russia was larger, but more backward). It had been preparing for war for years, often covertly and with the assistance of the USSR, while most of Europe was still recovering from the last war. When it attacked, it often had surprise on its side. How could they not have succeeded? Note how quickly Germany surrendered after D-day.
Inefficiency? Devoting rail capacity to Göering and Hitler's looted treasure and transport to concentration camps? Designing and building unreliable and unmaintainable tanks and V weapons? Canceling new weapons projects because "the war will be won before they are ready"? Hitler changing military plans on a whim? Sacrificing whole armies to hold unsustainable positions? Is this efficient? Hardly.
You might read "Double Cross" by Ben Macintyre. The Germans were awarding Iron Crosses to MI5 !
The Allies were far more efficient, if war can be ever be efficient.