Tehran is 6.5 hours ahead of São Paulo
Best overlap: 8:00 AM to 12:00 PM in São Paulo is 2:30 PM to 6:30 PM in Tehran.
For a call that suits both sides, look at 8:00 AM to 12:00 PM in São Paulo / 2:30 PM to 6:30 PM in Tehran. You share roughly 4 hours a day. That's enough for regular meetings, but treat the window as prime time and guard it.