Hello Proshat and welcome,
There are lots of ways to meet native english speakers. Here at englishforum we occasionally meet for events such as drinks, hiking, eating, etc. There's a hike tomorrow but only if you're single (and pretend to be over thirty).
There's a Zürich site at meetup.com and most of the group speak English: http://newintown.meetup.com/24/
Right now, the group is not active but this will change soon.
You can also join the Yahoo group called Expats-In-Zurich, which is an English speaking group for foreign residents. Beware though - it's a mailing list with a lot of "hot air" (i.e. nothing interesting) although occasionally there are events. There's a river cruise tomorrow, for example.
I'm sure there are more resources, but these are the ones I use.