I agree and disagree.
I agree, that you are born, or atleast develop at a young age, what your sexual tendencies are.
But there are factors, that decide, on what of that tendencys you act. These factors do not always yours to decide. Sometimes religion is a factor, or the law.
For example, I thougth I where gay. But that changed over time to being bi, and now I feel like loosing more ond more interest in humans all together. Maybe iam zoo exclusive in 10 years, maybe not.
While it's true that you are born with innate sexual tendencies and preferences, it's your experience through life that is going to dictate how you discover these things for yourself. You don't change from being gay to bi, for example. You discovered that you thought you were gay, you later discovered that you're actually bi. This isn't because your sexual preferences changed but it's because of how you perceived yourself based on your environment. With more experience and more evidence, your understanding broadens.
In 10 years perhaps you will become focused solely on zoo relationships as a result of your experiences with humans. That doesn't change the fact that you have an innate sexual attraction to humans in some form or another. Sexuality is fluid in that the way you process and learn more about yourself is through your life experiences, but deep down it is hard-coded into you. If it were possible to change, there's no reason that the vast majority of people wouldn't just change to fit the societal norm. Conversion therapy would actually work and it would be employed en masse.
Fetishes and kinks, however, are something that you learn or are conditioned into throughout your life. You are into those specific things for a reason even if you aren't entirely able to pinpoint it, there is always a root cause. This is the defining difference between someone who's into "bestiality as a fetish" and a zoophile. Also, you don't have to be exclusive to be a zoophile. That being said, many people will incorrectly consider themselves as zoo when they are really just a fetishist. There isn't really a glaring difference between the two of them from an outsider's perspective.
Hypothetically, let's say for instance that someone was born being either straight up repulsed or just not interested in humans and had a predisposition towards animals, but forced themselves to pursue human relationships because that's what society has taught them is correct. That person could later discover in life that they are zoo-exclusive, and that exclusivity isn't invalidated by the fact that they may have felt obligated to pursue relationships the way that society expects people to because they couldn't connect the dots until then. If a gay man marries a woman, has kids with her, all the while he has never experienced sexual attraction towards women, that doesn't mean he was ever straight for having been in a heterosexual relationship. At best, he may have repressed his sexuality due to religious or societal trauma. At worst, he's trying to convince himself that he's something he isn't because of an overwhelming feeling of guilt, shame, disgust for said religious or societal reasons.
Sexuality is a spectrum, and my hot take is that trying to fit yourself into a label is a waste of your time and energy. My own upbringing and experiences led me to discover the true extent of my sexuality later than most people. I realized at some point that I don't cleanly fit into any real label, and ultimately it doesn't matter. The only thing that matters is that I'm true to myself and those who I'm intimate with, human or animal. I don't have to prove that to anyone, I don't need a series of labels and pride flags to fuel my ego. I am what I am, I like what I like. That's that. I would go into more detail on my journey to provide more context as to how I reached this point, but I think this post is already pretty heavy.
If you grew up having a sexual attraction towards both humans and animals, and the attraction towards humans becomes weaker over time, that doesn't necessarily make you zoo exclusive (I'm speaking as someone who's in this boat as well btw). You could choose to pursue zoo-exclusive relationships, yes, but that doesn't mean that at your core you are exclusive. In other words, you can be a non-exclusive zoo that "practices exclusivity", but that doesn't necessarily mean that your attraction to humans has completely vanished. You could say this is overly nuanced, but sexuality is full of nuance, whether we want there to be or not.
In saying all of this, the point that I want to make is that labelling it is utterly fucking pointless and people put way too much weight onto these kinds of identity politics. Just be who you want to be, love what you want to love. Fuck what you want to fuck. You don't need anyone's approval for that beyond who you're being intimate with.