In case you are not heavily interested in aircraft (but then, why would you be active on this website ... ?!?) you also could take the train &head for downtown Zürich and have a stroll around - and maybe a short cruise on the lake.
Shopping is another option.
If you prefer to stay airside, (like in very inclement weather), there is a huge window to look out from Airside Center (opposite the shops); food outlets are located when heading into direction of B-gates.
Landside, but if not going onto a offical tour (observations desk or apron tour), you can stock up on supplies in two convenience stores and a proper supermarket located in the big building opposite the terminal building; head for "Parking" or "railway station". Atop the railway station you also will find a number of food outlets.
If time allows head for parking garage P6
located between the Radisson Blu hotel and Cargo center. From its upper levels one can spot descently and is a bit protected from the elements.
But above all, if time allows, go onto the guided apron tour which includes a stop at the famous runway cross. Be prepared to have CHF at hand for the tour. And bring your camera.
Carpe diem ! Life is too short to waste your time ! Keep in mind, that today is the first day of the rest of your life !