Germany would still be bled white to gain victory over the Soviet Union, getting a long, hostile border with the post-victory Soviet successor state that may or may not be engaged in actual direct or indirect warfare. Plus of course, partisans are going to be a constant headache, forcing a strong garrison just to keep those conquests under some form of control.
All the destruction means that Germany won't get all that much economic benefit from those territories without substantial investment in reconstruction. There's looting to be done, sure, but that doesn't help the German situation in the long run. How is Germany getting the food to feed the workers it needs to reconstruct local transport networks, mines, industry? How is it paying the farmers for that food? The Germans can certainly extort or requisition it, but that just boosts the hostility of the farmers and doesn't help win much improvement in food production. Starving the cities in the USSR in order to have food left over for German domestic and military consumption leaves you with few willing workers to reconstruct the primary products sector the Nazis were after in the first place.
With the war in the east more or less over, Romania, Italy and Hungary are also going to want to pack up their stuff and go home. They'll have to be given an incentive to stay and help with the partisan issue through Soviet loot, which simply adds to the expense.
The war's events have also left a massive chunk of German material and industrial output useless. Panzers won't help shoot down Allied bombers, or prevent allied buildup and landings across the Med. Retooling to build aircraft, u-boats, ships and AAA is going to be quite messy, and there's a potential question of availability for some materials.
What victory over the Soviets does do is give Germany the ability to reinforce its conquests in the west and south of Europe. That doesn't prevent future allied successes though, because the Germans have to be everywhere, while the Allies need only hit the proper weak points.
In any event, this at best delays Germany's defeat until nuclear weapons are available, possibly available in numbers. Even with heavy focus on air defenses, bombers are going to get through, and mushroom clouds pop up over German cities, and possibly troop concentrations until they surrender.
Japan probably avoids getting nuked, but instead is starved into surrender by bombing and blockade. If the entire government doesn't collapse, the potential for a communist revolution erupting among the starving and desperate population ought to focus a lot of minds on the inevitable.
When Japan goes down in say, 1945-46, those bombers, ships, supplies and aircraft can all be redirected to Europe in order to seize and pulverize every Axis island or peninsula the allies think they can hold. There'll be plenty of aircraft then to ensure Germany can be nuked early and often until the war is over.