First , honestly I think it's not that big of a deal , you know , Emma going out with Zak. It's just a first date and the fact that Zak thinks so lowly of Emma I doubt he'd even touch her...you guys know how he mentions her to his friends right ? ... 'fat ugly girl who is unattractive as fuck' and I also don't think he'd try anything nasty with her , given his ultimate goal is hitting the jackpot Charlotte , he'd do anything to keep Emma as happy as possible so he can get to the good side of Charlotte.
Second , Zak seems to be the guy who lives in his own world that everything around him will stay the way he demands...and he obviously has no idea that Emma actually has a bodyguard ( or he does , but it seems he doesn't )...also he doesn't even know that there is a word 'Strategy' exists...clearly he is not naive like Emma but he is a dumbass(while Emma is not) and I honestly don't think he'd make through even two dates.
He gotta spoil something in the first date since how he underestimates everyone around him there's a little chance that his horrid mouth might spill some beans that Emma could be able to pick up and it is more than enough for building a little suspicion and doubt onto his sudden interests and get a glimpse of his hidden intentions little by little or even faster with the help of MC.
Finally , MC already cooked up a little plan of his , you know mirroring Emma's phone , he'll be surveilling her phone conversations or he might come up with a better one. This will make plucking the prick Zak out of the way much easier. At the end of the day Zak is nothing more than a little prick.