Tehran is 3.5 hours behind Ho Chi Minh City
Best overlap: 12:00 PM to 6:00 PM in Ho Chi Minh City is 8:30 AM to 2:30 PM in Tehran.
Target 12:00 PM to 6:00 PM in Ho Chi Minh City, which lands at 8:30 AM to 2:30 PM for the Tehran side. Tehran is 3.5 hours behind Ho Chi Minh City, but you'd hardly notice — 6 hours of shared hours makes this feel like working in neighbouring time zones.