Ever since Zombie Villagers were added back in 1.4.2, mobs have been able to change types. While zombie villagers keep their trades when converting between a villager and a zombie, their random name is shifted. This was found with Piglins for me, and a simple method at that.
1. Spawn a Piglin.
2. Point at it, then autofill /data with get, entity, and then the targeted mob's randomly generated name.
3. Let it zombify.
4. The "No entity was found" error message will appear in chat.