So everyone who knows a little bit about biology has a vague idea that after catastrophic events or Apocalypses there's always a boom in the variety of animals which evolve.
Creatures like us only exist as result of many different catastrophic events. And we were never alone, when we had scales and walked on four limbs there were dozens of other related species to us which eventually evolved into something else. When we climbed trees to eat fruits, we were just one of the many options to choose from the ape kingdom and when step foot on the ground we were just one of the many hominids on earth.
This is why it seems kind of unlikely to only have one strand of zombies.
Do you know the meme about Elves? How everyone started using elves in their settings that it became ridiculous and they made water elves, dark elves, light elves, void elves, blood elves, shadow elves, high elves, sun elves.
I wanna extend this to zombies, how many different types of zombies can one have?
Zombie= entities which were once humans that have turned into other beings with increased aggresivity that attack healthy humans to infect them. By this definition zombies are indistinguishable from some types of vampires or werewolves so to make it more specific I will give the limitation that zombies have no superpowers which could be reminiscent of vampirism or lycanthzombies.
To count as different types of zombies they must be from different species/origin and competing for reproduction, even if passive there will be competition. It doesn't matter if one type of zombie being slower or with less infectivity creates less zombies, even if there are only a few of a certain species I want at least more than two different species of zombies maintain a certain balance where one does not cause the extinction of the other.