Let's look at some of the reasons people say zoophilia and pedophilia are the same.
Consent - Most people believe that neither children nor animals can consent to sex because neither are aware of what sex is or what it entails or means. The simple fact is, once an animal reaches sexual maturity, he or she is aware of what sex is and how it works, and therefore capable of consenting to or denying sexual contact. Whether children have this ability before they are sexually mature, what constitutes sexual maturity in humans, and when children stop being "children" are questions that belong somewhere else.
Predation - Largely because animals and children are both seen as "helpless", both zoophilia and pedophilia are thought to be predatory behaviors. However, animals are quite capable of making their wishes known, and will do so. Therefore, zoophilia is not an inherently predatory behavior. Sexual predation, like rape, has very little to do with the sexual act itself. It is a far more complex behavior and often does not make distinctions based on attraction. In other words, a sexual predator might very well prey on animals as well as children, for the next reason we will discuss.
Reporting - One thing which sets animals apart from humans is that they cannot "tell on" someone who has abused them. We can see the results of abuse but there is often no way to know any specifics because of the communication gap between humans and animals. Children are able to tell others what happened, but often they don't know exactly what happened and/or they don't know that it is wrong, or why it is. So in both cases, abuse goes unreported.
Sexuality - In both zoophilia and pedophilia, sex is involved. Sex with beings that most people do not view as being sexual, therefore such activity must be wrong. In the case of rape or any kind of abusive behavior, it is most definitely wrong, in both cases.
Perception - The most-often used reason is usually the one that's overlooked. A vast majority of pet owners perceive their animals in the same way they perceive their children. However, humans almost never see animals as beings with any real emotional or intellectual capabilities beyond bringing in the newspaper. People forget that animals reach sexual maturity far faster than humans do, and that mature animals probably have a somewhat different view on life, just as humans do as they get older. This view of animals as helpless, child-like beings doesn't do either animals or children justice.
So are zoophilia and pedophilia the same? Not really. Do the people involved necessarily have the same mindset? Maybe. However, the same can be said of any population, since sexual predation is by no means confined to atypical interests.
That being said, Heather, you should definitely try to understand what exactly your boyfriend means when he says he is into zoophilia and how he feels about it, so you can make an informed decision. He may need professional help, or he may need something else. I wish the two of you the best of luck.