Minecraft wiki entry for Zombie, associated text: Zombie villagers have a 5% chance of spawning in place of zombies, and may also spawn from a villager killed by a zombie. The chance of a villager turning into a zombie villager when killed by a zombie or zombie variant depends on the difficulty level. Zombies spawned from a spawner are never zombie villagers,‌[JE only] although zombie spawners are able to produce them.‌[BE only]