I was very impressed with the service and quality offered by
Nourished by Otillie - she does these really amazing apéro riche platters of wholesome and yummy food that look totally different from your usual "apéro fare" found in Switzerland. However, she is based in Lucerne and would charge you for travel time but she will come to your place and either use what you have lying around to create a buffet or she will bring her own platters and decor and you can also arrange for her (or one of her staff) to stay during your event. Obviously, all this does not come at a bargain price and "economies of scale" come into it, the more guests you need catering for the less it costs per head but then I have no idea what budget you are looking at.
I also recently got a flyer in my letterbox from
a guy who offers a range of catering and culinary events, I've linked to his catering choices (only available in German but based on his profile he will speak English), his standard delivery area is Oerlikon/Glattpark/Wallisellen/Kloten but I am sure that he would go further afar for a surcharge. Not tried this stuff myself but it sounds nice.
And of course, I second the suggestion of Laughing Lemon, delicious food and a great chef with inspiring passion behind it all.