In many forms of media, they depict the military of Nazi Germany was this well-coordinated and very elaborately crafted military force which may be the case when looking into its successes in the early years of the warlike the occupation of France, Norway and a portion of Russia.
And there is a lot of credit to Blitzkrieg as it was one of the most advanced version of modern military tactics and an upgrade compared to that of WW1.
But in the later years of the war, the Nazi forces kept on being pounded with failures like the British campaign in Africa, the Axis' failure to conquer the island of Malta, Greece being liberated and the Red Army pushing against the Eastern Front while the Allies pushed from the West.
Was this portrayal of the Germany Army being this well-oiled machine actually accurate or was it a form of German propoganda?
While there's some truth to the sense that the German soldier and officer was generally more competent and professional than his Russian counterpart, this tends to be vastly overstated.
Blitzkrieg (the Schwerpunkt doctrine) was always a gamble, as it focused on breaking one point (think of a battering ram) and then reinforce and "flood" that point to encircle enemy formations.
But if we compare Poland and the Western front to the Eastern front, we discover the main problem with Schwerpunkt.
In Poland and France the Germans had essentially won before the Polish could effectively mobilize their manpower, and had destroyed a large part of the French Army by encirclement and compelled France’s defeat even though France could have, given enough time, replaced these losses, as the Soviets did during Barbarossa and Typhoon.
In the same vein the Germans could probably have replaced the losses even of Uranus and Bagration had the tempo of the Russian advance not been so relentless. By the time the Germans had cobbled together another front the Russians had already broken through it, as the Germans did to the French on the Somme and Aisne during Red. They were accordingly given no time to rebuild their armies with manpower reserves.
Soviet doctrine was very sophisticated and after the emergence of very competent generals like Konev and Rokossovsky the Red Army became one of the most professional and effective armies in the world.
Deep Operations was very sophisticated. Unlike the German concept of Blitzkrieg, where one main axis of attack was determined upon, Deep Operations consisted of multiple attacks on multiple axes and any that succeeded were exploited in depth.
The biggest reason why the Germans has been considered an almost invincible force is two-fold:
The former German officers writing for the Army Historical Division dominated the perspective of the Soviet-German War and it was full of self-serving racist nonsense. This has since been substantially altered following the fall of the Soviet Union. I guess one could say that the one-sided German accounts were definitive.
As Randell Wells Jr. points out in "Tearing the Guts Out of the Wehrmacht" by 1943 the disparity in losses between the Soviets and Germans had become much more narrow. And losses in the first years were inflated due to large numbers of captures, especially during Barbarossa when the element of surprise was entirely on Germany’s side and the direction of the German advance was guessed wrong by STAVKA.
I'm not sure if this is exactly what you wanted, but some further sources I can highly recommend is "Myths and Realities" by David Glantz, "Wages of Destruction" by Adam Tooze, "How we didn't win the war...but the Russians did", an article by Norman Davies.
If you have further questions, don't hesitate to give me a call.