It is easy to dismiss him as creepy. General Zorrof is ambitious, civilized and intelligent. He is ambitious because he wants to be the best. Hunting is so important to him that he had to choose the most difficult game, man. Although he has hunted all over the world, he became so good at it that he needed to find more challenging prey.
Zorrof is also civilized. Although he kills human beings, he considers himself civil. He lives like a gentleman and behaves like one even while hunting. He is careful in his speech and mannerisms. He follows rules while hunting, and is not just murdering people.
Finally, Zorrof is intelligent. He has figured out how to hunt human beings, realizing that they will offer him a challenge. His island is set up specifically to entrap people. When he does entrap Rainsford, he is able to hunt him even though Rainsford eventually wins.