"Among the animals"
because it ends with zwierz-ę . ę eniding nouns have either -ąt or -on pural genitive. this one follows IV declination https://pl.wiktionary.org/wiki/Aneks:Język_polski_-_deklinacja_nijaka_IV
You could actually hear "zwierzów", I guess, but that would be coming from a word 'zwierz'. This, I think, is used rather colloquially, although the dictionaries claim that it's used for the exceptionally big animals. Or in poetic contexts. So anyway, not a standard wording.