@EvieTJK Please try switching to the Sims 3 camera and back, quitting the game and restarting in between, and let me know whether zooming works in either mode. If it doesn't, go into Documents > Electronic Arts > The Sims 4 and move options.ini to the desktop. This will reset all your in-game options; if it doesn't help (switch camera modes again), you can put the old options.ini back.
And please make sure you're not touching the trackpad in any other way. I know it seems obvious, but some trackpads can be very sensitive, and it's always possible your hand position when playing Sims 4 puts you slightly in contact with it.
