Shenzhen is 1 hour ahead of Hanoi
Best overlap: 8:00 AM to 5:00 PM in Hanoi is 9:00 AM to 6:00 PM in Shenzhen.
Hanoi and Shenzhen overlap from 8:00 AM to 5:00 PM (Hanoi) to the equivalent 9:00 AM to 6:00 PM in Shenzhen — that's your meeting window. Plenty of room to work with: 9 hours of daily overlap means you can prioritise people's preferences over the clock.