Chennai is 2.5 hours ahead of Riyadh
Best overlap: 8:00 AM to 4:00 PM in Riyadh is 10:30 AM to 6:30 PM in Chennai.
Shoot for 8:00 AM to 4:00 PM in Riyadh; your Chennai colleagues will see that as 10:30 AM to 6:30 PM. The overlap is wide at 8 hours, so you can protect mornings for deep work and still find plenty of meeting time.