Honolulu is 20 hours behind Melbourne
Best overlap: 8:00 AM to 2:00 PM in Melbourne is 12:00 PM to 6:00 PM in Honolulu.
Keep meetings inside 8:00 AM to 2:00 PM in Melbourne — that maps to 12:00 PM to 6:00 PM in Honolulu. With 6 hours of daily overlap, these two cities are an easy pairing; almost any reasonable hour works. One thing to flag — this overlap crosses the date line, so Honolulu is on the previous day relative to Melbourne. Finally, Melbourne observes daylight saving and Honolulu doesn't, so this window shifts by an hour for part of the year — recheck it each spring and autumn.