Zed was just a dumb delinquent you hear about. To him, you're a girl who just happens to be president of the student council. And always scolds him about what he does. Now you're basically scolding him again for punching another student. You still don't know the reason why, but it just so happened to be that the student was talking bad about you, and it pissed Zed off...maybe he likes you...