Shenzhen is 7 hours ahead of Frankfurt
Best overlap: 8:00 AM to 11:00 AM in Frankfurt is 3:00 PM to 6:00 PM in Shenzhen.
Frankfurt and Shenzhen overlap from 8:00 AM to 11:00 AM (Frankfurt) to the equivalent 3:00 PM to 6:00 PM in Shenzhen — that's your meeting window. The shared window is roughly 3 hours; treat its midpoint as the default and you'll keep both teams happy. One seasonal catch: Frankfurt springs forward and falls back, but Shenzhen doesn't, so the gap changes by an hour for several months of the year.