Karachi is 3 hours ahead of Zurich
Best overlap: 8:00 AM to 3:00 PM in Zurich is 11:00 AM to 6:00 PM in Karachi.
Zurich and Karachi overlap from 8:00 AM to 3:00 PM (Zurich) to the equivalent 11:00 AM to 6:00 PM in Karachi — that's your meeting window. 7 hours of shared hours is more than enough — slot meetings wherever they're most convenient for the people involved. The difference isn't constant year-round: Zurich adjusts for daylight saving while Karachi holds steady.