Istanbul is 5 hours behind Shenzhen
Best overlap: 1:00 PM to 6:00 PM in Shenzhen is 8:00 AM to 1:00 PM in Istanbul.
For a call that suits both sides, look at 1:00 PM to 6:00 PM in Shenzhen / 8:00 AM to 1:00 PM in Istanbul. With 5 hours of overlap, 1:00 PM in Shenzhen (8:00 AM in Istanbul) is a comfortable, repeatable slot for both sides.