Tehran is 6.5 hours behind Melbourne
Best overlap: 3:00 PM to 6:00 PM in Melbourne is 8:30 AM to 11:30 AM in Tehran.
For a call that suits both sides, look at 3:00 PM to 6:00 PM in Melbourne / 8:30 AM to 11:30 AM in Tehran. Around 3 hours of overlap is enough to work comfortably, as long as meetings don't drift to the end of one team's day. Remember that Melbourne shifts for daylight saving and Tehran doesn't, so recalculate the overlap after each clock change.