Hanoi is 4 hours ahead of Tel Aviv
Best overlap: 8:00 AM to 2:00 PM in Tel Aviv is 12:00 PM to 6:00 PM in Hanoi.
Plan around 8:00 AM to 2:00 PM in Tel Aviv, which is 12:00 PM to 6:00 PM in Hanoi, to catch everyone during office hours. The overlap is wide at 6 hours, so you can protect mornings for deep work and still find plenty of meeting time. Don't be caught out by clock changes — Tel Aviv observes daylight saving and Hanoi doesn't, so the offset varies by an hour through the year.