Shenzhen is 2.5 hours ahead of Chennai
Best overlap: 8:00 AM to 4:00 PM in Chennai is 10:30 AM to 6:30 PM in Shenzhen.
For the smoothest call, aim inside 8:00 AM to 4:00 PM in Chennai, i.e. 10:30 AM to 6:30 PM in Shenzhen. Shenzhen is 2.5 hours ahead of Chennai, but you'd hardly notice — 8 hours of shared hours makes this feel like working in neighbouring time zones.