Iron farm and villager breeder in one

A combined iron farm and villager breeder for four villagers and one zombie, with no redstone. Three villagers sleep above a drop into lava and the zombie panics them into spawning golems, while a fourth farms carrots to feed the breeder. It makes about 300 iron an hour and two baby villagers each Minecraft day. Java only.

Panicked villagers will not breed and will not sleep, so the two halves fight each other. Keep an extra layer around the zombie's head so you can open the trapdoor for iron and close it for breeding, or put a fence post in front of the zombie to hide two of the beds from him so both run at once.
If golems stop after a while, block the zombie's line of sight at night so the villagers get one uninterrupted night, then open it again.
Baby villagers walk into the zombie's box. Move the zombie chamber one block further out, or put carpet on the trapdoor he stands on.
Lightning turns a villager into a witch. Put a lightning rod nearby, or roof the area.
Golems spawn on farmland on current versions. Put glass over the crop field and a glass block on every trapdoor.
Put the composter in the middle of the field so all the farmland is in the farmer's range, with a block on top so he does not jump onto the crops.