Long layover in Zurich airport | looking for something to do

I see no reason to go to the expense of a private driver. You can get trains to Zurich almost continuously and it is only about 10 to 15 minutes from the airport train station. Luzern is just 1 hour away. If your luggage is checked through to Sicily and you have boarding passes, you could cut it as close a 1 hour before flight time to get back to the airport.

There is not that much to see where you would need to hire a private driver, which like everything else in Zurich would be pretty expensive.

We will probably not check our bags, so we would have to carry them with us. Is there any place to leave our bags while we do some sightseeing in Zurich?

There are definitely lockers at the airport train station in Zurich. It costs about 10CHF per locker all coins. it is located where you buy your ticket to the city before you go down stairs to the train platforms.

There are 2 different locker sizes at Zurich Hbf, at various rates. The largest size is 9 CHF and took a full size suitcase, back pack, and computer bag, with room to spare.

Hertz, you say "We will probably not check our bags, Does this mean you have hand luggage only?

Depending on the timing, I would suggest Luzern. It would pan out like this (times from Swiss Railways website: https://www.sbb.ch/en/ ):

• 08:00 Land Zürich (I am guessing this is aprox what you mean by "early morning").
• 09:00 Through immigration and emerge at airport arrivals. This would vary depending if you flight was early or late, or nay backup at immigration.
• 10 minutes to walk to station and buy ticket (CHF 60 return). Trains to Luzern at: 09:18, change Zürich HB, arrive Luzern 10:25 or 09:47 direct arrive 10:47. If you are earlier or later, the trains are the same time past each hour.
• 11:00 - 14:00. 3 hours in Luzern, including lunch.
• 14:10 depart Luzern by train, arrive Zürich airport 15:13, which should be OK for a 17:00 flight if you already have your boarding card.

There is a left luggage facility at Luzern station.

If you want to see what Luzern is like, see this 360° panorama: http://tour.luzern.com/360/en/
The station is to the left of the bridge, the old town to the right.

A private driver is a bad idea because:
A) It would be painfully expensive.
B) He cannot take you into the city centre (pedestrianised), nor stop and wait while you get out to look at things or visit a restaurant.

For a layover, what I would do is:

• take train from airport to Zurich hauptbanhof (main train station)
• the National Museum of Switzerland is right across the street from the station

Walking around Zurich is a very a pleasant thing to do. I would recommend visiting the Fraumunster Church to see the Chagall's stained glass windows.

I would stash luggage in a locker and walk around Zurich.
As Darrenblois says, the Landesmuseum Zurich is excellent.
Maria is correct, walking around Zurich doesn't suck.
We have enjoyed walking the Bahnofstrasse to the lake and taking a boat tour of the lake. Sprungli is definitely worth a stop for a few Luxemburgerli along the way!

Or, you could cross the river at the Bahnof and walk around the Aldstadt and along the river.

You will be on vacation in Switzerland. It is hard to make a bad move.