Oslo is 7 hours behind Shenzhen
Best overlap: 3:00 PM to 6:00 PM in Shenzhen is 8:00 AM to 11:00 AM in Oslo.
Your shared working hours run 3:00 PM to 6:00 PM in Shenzhen (8:00 AM to 11:00 AM in Oslo). You've got a decent 3-hour window. Set a recurring time near 3:00 PM in Shenzhen (8:00 AM in Oslo) and stick to it. Watch the DST gap — when Oslo changes its clocks and Shenzhen stays the same, this window slides by an hour.