i am trying to get a "super" type zombie to spawn on my overworld.

But nomatter where i put this i cant seem to get it to work.

I tried either "minecraft:zombie_villager" or just "Zombie" but neither work.

Latest attempt was :

https://hastebin.com/woconebame.json

but that didnt work at all.

Can you help me how i can get a strong zombie(villager) to spawn in the night with a higher chance than normal mobs? I am lost xD

P.S MC 1.12.1