Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Lerwick to Belfast as you normally would.
Lerwick All Airports (SDZ) is the airport you will fly out of if you book a flight from Lerwick to Belfast. You should not have trouble finding flights to Belfast from All Airports; the airport handles an average of 0 outbound flights to Belfast per day. You should also have plenty of airline options to choose from since 0 airlines have flights from the Lerwick airport to Belfast. It is only a 0.2 mi journey to All Airports (SDZ) from Lerwick’s city center.