I stayed with Peter and Engin over the time of my summer internship in Zurich. They were very generous and gracious. One time in particular I had friends over for dinner, and not only did they set the table beautifully for us, but they also gave us two bottles of wine as a present.
The flat is in a beautiful location, close to the historic center of Zurich, and close to many hilly paths excellent for runners. It is also literally across the street from a tram stop, and there is a cherry tree in the back garden.
Eating my muesli on the balcony in the mornings was a great pleasure during my stay, as was running into either of the hosts on my way in or out.