Wear on soft revolver frames can show up in a number of places, such as where the cylinder crane swings in and out and at the recoil shield where the cartridge case backs up under pressure. I have seen zinc alloy frames with indents in that area deep enough to prevent the cylinder from turning. In addition, they will stretch under firing stress, eventually becoming inoperable.
It depends a bit on what is expected. For a defense gun, where the owner never intends to fire more than a few dozen or at most a few hundred rounds, zinc alloy will probably stand up as well as the best steel.
But the alloy frames will definitely show stretching, peening, and wear after a thousand rounds or so and break or begin to go seriously awry after that. Basically it is once again of getting what you pay for.
I have to note that much of the above also applies to aluminum alloy frames, though the better aluminum alloy guns will last longer than any zinc alloy guns.
Jim