On the contrary, given the current strength of the Beastman Tribe on this continent, it wouldn't be implausible for them to assimilate Zhou Tian, so long as they were powerful enough.
Thus, even though one's race instinctively feels suspicious towards outsiders, in view of Zhou Tian's reluctance to submit to other Beastmen, choosing to serve the Elves - who are hostile to the Beastmen - surely trumped serving the Beastmen residing on this continent.
Meanwhile, although the relationship between Beastmen and Elves isn't particularly good, both races' empires had fragmented after their divisions. At this time, regardless of which continent they were on, both Beastmen and Elves no longer had many conflicting interests in this present epoch. Contrarily, in comparison to the friction between them, internal strife within the Elf and Beastman Clans couldn't be ignored.