Best overlap: 1:00 PM to 6:00 PM in Brisbane is 8:45 AM to 1:45 PM in Kathmandu.
Plan around 1:00 PM to 6:00 PM in Brisbane, which is 8:45 AM to 1:45 PM in Kathmandu, to catch everyone during office hours. Since Kathmandu is 4.25 hours behind Brisbane, the workdays overlap by around 5 hours; 1:00 PM in Brisbane (8:45 AM in Kathmandu) makes a reliable recurring slot.
The US to Australia gap runs 14 to 19 hours depending on the month, and someone is always in tomorrow. Exact overlap windows for every US coast, the double-DST trap, and a rotation rule that keeps it fair. -