Zack is an odd guy, and not very nice... I'm sorry you feel the pacing is off, I just found it fitting that a sociopathic horndog would initiate something if he caught someone watching porn - although I'd be happy to hear any feedback you may have regarding this

What can I do better, and how?
Even a sociopath horndog would groom their victim a bit before sticking it in, one would think.
To make this less 'choppy', you could have a couple of interactions happen that are in-character, but give the player more of an idea of wtf is happening, i.e.
- events where the MC finds their room oddly disturbed, but not to a degree where they know what's going on
- daily chores where the MC has to spend a time slot to do housekeeping (with peeping/casual molestation events?) or get punished by humiliation that eventually escalates
- leverage events in which Zack uses whatever material he has (showering media? couch masturbation? wardrobe malfunctions while doing chores?) to make the MC do things the MC might not do (depending on corruption) - like sending lewd selfies, etc
This is just me spitballing to make the point that Zack could use a little fleshing out