In the Overworld, zombies spawn in groups of 4 at a light level of 7 or less.
In deserts,
all zombies exposed to the sky have an 80%[JE only] / 70%[BE only] chance to be replaced by husks, a zombie variant. Zombies that are not husks or drowned have a 5% chance to spawn as a zombie villager while all zombie variants also have a 5% chance to spawn as a baby zombie type.
Baby zombies have an additional 5% chance of spawning as a chicken jockey.[JE only] When spawning, a baby zombie may spawn on top of a nearby chicken. [JE only]
Baby zombies have a 15% chance to want to be a jockey, and if they do, then upon nearing the player and before attacking, they check for one of the following and mount it: adult zombies, chickens, sheep, cows, pigs, llamas, ocelots, foxes, pandas, mooshrooms, untamed cats, untamed wolves, horses and variants, spiders and cave spiders.[BE only]
