The galaxy is a big place - I would say there is room for a 'counts as' Zoats equivalent.
Or - at some point the Zoats (or something similar) were absorbed by the Hive. You could represent them before that?
As a side note, one of the things I'm lest fond of with the more recent 40k lore is that almost every alien that you find in the galaxy is now related in some way to Tyranids. Catachan Deathworlds? Due to Tyranid spores. Genestealers? Advanced guard for Tyranids. That giant underwater Kraken that Russ fought when a young Primarch? Probably a Nid too! I believe there are others. IMO it's a real imagination-fail, it's overly defining the 40k universe and removing the mystery from what should be a massive, dark and unknowable place. And most importantly leave some space for hobbyists to define a bit of that mystery themselves.
The Tyranids are so effective at absorbing other species that they've actually started hoovering up the lore too!
