Shenzhen is 4.5 hours ahead of Tehran
Best overlap: 8:00 AM to 2:00 PM in Tehran is 12:30 PM to 6:30 PM in Shenzhen.
Plan around 8:00 AM to 2:00 PM in Tehran, which is 12:30 PM to 6:30 PM in Shenzhen, to catch everyone during office hours. Shenzhen is 4.5 hours ahead of Tehran, but you'd hardly notice — 6 hours of shared hours makes this feel like working in neighbouring time zones.