The scene where Zack put Erica in the closet and gets Harold to confess the truth, wasn't that a terribly traitorous action? Don't get me wrong am a big fan of Harold X Erica ship and both of them are my favorite characters but Zack didn't know anything about Erica beside the fact she's a from a noble family and a his fiance and while his intention might've been benign that still doesn't excuse him