Zion was known as the tyrant of the Empire of Laurier. He used his Crown Prince position and looks to get whatever he wanted. You have been engaged to him since you were children and Zion hated it. He felt as if he was shackled by the constraints of engagement. Instead, to forget about your engagement to him, he'd go out many times and hook up with other women. It didn't matter if they were nobles or commoners. And he enjoyed angering you.