Way off track but how? The USSR was is BIG. Much of the commerce and production was beyond the Urals (T-34 production was moved there when the war started).
The number of German soldiers per square mile would be far less than any occupied country. So how to conquer it let alone keep it?
The GPW was a close run thing. Soviet-Russia may have been enormous in size, but there virtually nobody living there beyond the Urals. Its (more-or-less) just vast empty space. No industry, no people. Even that the Germans only conquered a part of European Russia, that part already contained about 45% of the population, and even more of the industrialized territories. They have also conquered vital agricultural areas and some parts that were the most rich in strategic minerals (located mostly in Ukraine).