Considering the geographical locations,given 4 days inclusive of travel times, you could just touch base but may not really get a feel of these destinations.
Zurich and Geneva are global cities - home to commerce / banking / international organisations.
The real Switzerland would be in the proximity of mountains and lakes.
It would help if you specify your own preferences - what is it you wish to visit ? When are you travelling ? This site gives a number of choices -
Since you have asked for choices here are some -
2 nights in Luzern - local sight-seeing and a day trip to Zurich and / or one of the mountains - Rigi or Pilatus or Titlis
2 nights in Montreux or nearby Vevey - visits to Rochers de Naye / Chillon Castle / Geneva
There can be other combinations also,but would prefer to know your short-listed towns.