Bucharest is 1 hour ahead of Vienna
Best overlap: 8:00 AM to 5:00 PM in Vienna is 9:00 AM to 6:00 PM in Bucharest.
Both offices are open during 8:00 AM to 5:00 PM Vienna time, which is 9:00 AM to 6:00 PM in Bucharest. The 1-hour gap barely gets in the way — you've got 9 hours of overlap, so pick whatever time fits the agenda.