I don't think either came first for me. I had always felt a certain way about animals, I always got along better with them than my peers, but I didn't understand it, and I didn't know zoophilia was a thing. I also had an interest in anthropomorphic characters, even as just a non-sexual, fandom thing. I loved all the possibilities for self expression, the diverse potential of being non-human. I was obsessed with media with talking animals or animal-like characters, as well as media featuring transformation (The Swan Princess was my favourite movie, and I loved anything with mermaids). I was enamoured with media that featured characters that could communicate with animals, and wished I could do the same. I think furry and zoo really went hand in hand as I grew up.
I discovered furry as a teenager. My involvement in the fandom was non-sexual to start with, I just loved art and roleplaying. I actually won a local youth art competition with a furry painting haha. I had furry friends in high school, and teenagers being teenagers, we eventually found the adult artwork, and something just clicked for me.
It didn't take me long to realise just how much I loved feral yiff. I had also been incredibly curious about animal reproduction for some 'unknown' reason... Feral yiff gave me an 'excuse' to indulge my curiosity. It didn't take me long to accidentally stumble across zoo porn, and instead of seeking more of it (I felt like I had discovered something forbidden, I was kinda scared), I instead decided to look up *why* somebody might do that. Which led me to read about zoophilia in general. Something finally made sense, my affinity with animals had an explanation, though I was still too ashamed to explore further. I spent the next few years going through phases of lurking, then abstaining cold turkey and denying it, and lurking again.
With the pandemic throwing things out of whack, I had more time with my own thoughts and this wasn't so avoidable anymore. Upon some self reflection late last year and earlier this year, I decided to bite the bullet and stop hiding from the community and from who I am.
This probably went a bit off-topic, I have a habit of rambling, but it's good to work through my own feelings, so whatever.
TLDR: I've been both since I can remember really, but I only accepted my zoophilia a while after being a furry. Neither are purely sexual for me.