Wellington is 8 hours ahead of Islamabad
Best overlap: 8:00 AM to 10:00 AM in Islamabad is 4:00 PM to 6:00 PM in Wellington.
For the smoothest call, aim inside 8:00 AM to 10:00 AM in Islamabad, i.e. 4:00 PM to 6:00 PM in Wellington. The overlap barely stretches to 2 hours, so reserve it for what really needs a live conversation and handle the rest async. Daylight saving complicates things slightly: Wellington observes it, Islamabad doesn't, so the difference flexes by an hour part of the year.