You can get zombie villagers, they will spawn if you have mob spawning enabled and you can cure them so they become a villager.
Iron farms do not work as Nobleza stated The only way to effectively get iron is buying it, a rare spawn chance from your cobble generator, inside key crates, and in rank kits.
The iron drop is limited tovombie villagers specifically, and those zombies only spawn by natural means. The droprate is moreover the same as the droprate from vanilla zombies. I once tried to set up a villager farm to be raided by normal zombies, hoping the villagers would turn into villager zombies to farm iron. But zombies don't attack villagers.
Thank you for your thread on a recent query! It seems like it has now been resolved. This thread has been locked moved to Help Archive.