I do kind of think that Zach is a bit of a bad guy. He could have gone a different way, but people in his life were too indifferent to his worst behaviors and I was pretty done with him by the time he was spying on the girls in the locker room. It was not that one action that convinced me but it was a part of a larger pattern of disrespectful and depraved behavior. The more he pushed things and the more that people let him get away with the more he was susceptible to Ethan scooping him up and making him his henchman, which is what he is now. It is a shame because he probably wants to be a better person deep down, but he feels like he isn't getting the love he deserves and that can really embitter a person. But people are not inherently good or bad we can only judge them by their deeds.