Hanoi is 6 hours ahead of Prague
Best overlap: 8:00 AM to 12:00 PM in Prague is 2:00 PM to 6:00 PM in Hanoi.
Target 8:00 AM to 12:00 PM in Prague, which lands at 2:00 PM to 6:00 PM for the Hanoi side. Hanoi is 6 hours ahead of Prague, so the practical overlap is about 4 hours — generous enough for meetings, tight enough to be worth booking ahead. Note that Prague follows daylight saving while Hanoi stays put, so the times above drift by an hour seasonally.