Chennai is 6.5 hours behind Wellington
Best overlap: 2:30 PM to 6:30 PM in Wellington is 8:00 AM to 12:00 PM in Chennai.
If you set up a recurring sync, 2:30 PM to 6:30 PM in Wellington (8:00 AM to 12:00 PM in Chennai) is the natural home for it. You share roughly 4 hours a day. That's enough for regular meetings, but treat the window as prime time and guard it. Because Wellington and Chennai don't both observe daylight saving, plan to re-check the overlap around March and November.