If i get a major in Biology 4 year college but I want to become Zoologist which is certain kind of would then go another and study Zoology?

A biology major is an excellent foundation for becoming a zoologist. You don't need a separate zoology major *after* your biology degree. Zoology is a specialization *within* biology.

While some universities offer a zoology major directly, a biology major with focused coursework in zoology-related areas (e.g., animal physiology, ecology, animal behavior, genetics, evolution) will prepare you well for graduate studies in zoology. Most zoologist positions require at least a master's degree, and many prefer a PhD. It's during your graduate studies that you'll deeply specialize in zoology.