Quick question, which version and which flavor of Zorin are you running? (i.e. Zorin 15.3 Lite)
I think this is a problem that exists on Zorin 15.3 Lite because it doesn't have the Synaptics driver pre-installed. Running the command mentioned by Storm should install it for you and fix the problem.
Or does the touchpad work but you can't tap on it? Does hard clicking work?
@anon37206250 The way I read the OP, it was the hard touchpad buttons that do not work, no mention of tapping soft buttons on touchpad area. I assume OP will confirm this.