Why Germany and the Soviet Union struggled to bomb each other

How effectively did Germany and the Soviet Union strategically bomb each other?

Not very effectively, because the distances were enormous and much Soviet industry had moved beyond the Urals.

Germany and the Soviet Union both attempted long-range bombing, but geography imposed severe limits. Soviet aircraft faced great distances to important German targets. The Soviet relocation of much industry to the far side of the Urals made the German problem even harder. Strategic depth therefore protected production in a way that tactical success near the front could not easily overcome.