I found a bug that exist in game long time.
Zombie villagers hasn't got their profession skins, or visual presentation of their professions.
I can explain, when I make, for exemple, librarian villager zombie, it loses his profession skin, but biome skin doesnt change. I made librarian villager and made it zombificated, but he lost his visual presentation of profession. Then I made swampland villager with other profession and his zombificated version also hasn't got profession. It's not big problem, but its not cool
I hope you'll solve it
Good luck, Mojang Studios.