Hanoi is 1.5 hours ahead of Delhi
Best overlap: 8:00 AM to 5:00 PM in Delhi is 9:30 AM to 6:30 PM in Hanoi.
Plan around 8:00 AM to 5:00 PM in Delhi, which is 9:30 AM to 6:30 PM in Hanoi, to catch everyone during office hours. Hanoi is 1.5 hours ahead of Delhi, but with 9 hours of common ground you can hold morning or afternoon meetings without anyone working odd hours.