The Bug:

Z-fighting occurs on the backs of villagers' and illagers' heads when they look up or down.

Just for clarification reasons, this issue can be seen on all villagers regardless of their biome skin and profession. It's more easily visible on unemployed villagers with desert or swamp biome skins due to them not having outer skin layers around the affected area of where this problem can be seen.

As for illagers, the z-fighting is hard to see on illusioners, vindicators, and evokers due to them having outer skin layers, but is still present nonetheless. On the other hand, pillagers don't have any outer skin layers around the affected area of where this problem can be seen, so the z-fighting is easily visible on them.

Steps to Reproduce:

1. Summon a villager that's looking up by using the command provided below.

   /summon minecraft:villager ~ ~ ~ {NoAI:1b,Silent:1b,Rotation:[0f,-45f],VillagerData:{type:"minecraft:swamp"}}

2. Look at the back of its head closely.
3. Take note as to whether or not z-fighting occurs on the backs of villagers' and illagers' heads when they look up or down.

Observed Behavior:

Z-fighting is present.

Expected Behavior:

No z-fighting would occur.