Trained dog attacked saved (former zombie) villager

I have a zombie villager that originally spawned in an abandoned village (he was stuck in one of the houses). I saved/healed that zombie villager back to normal and gave him a job (I'm actually repairing and repopulating an abandoned village as my home base).

I then tamed a dog that spawned in the town.

The tamed dog proceeded to start attacking the (former zombie) villager.