If any zone LED pin is set HIGH, the buzzer pin is set HIGH, too. Right?
Create 3 instances of the Button class, one for each zone.
You probably want three functions (although you really only need one) that will set the zone LED pin HIGH, if the zone switch has changed state (Button::uniquePress). Set the buzzer pin HIGH, too.
Then, create a 4th function that checks the reset switch state, and turns off the buzzer pin if the reset switch state is HIGH.
By the way, function names, like variable names, should be meaningful. checkZone1() means a lot more than loop1().