Teddy Sears is currently under contract with Fox for his part on 24: Legacy, so returning to The Flash on The CW isn’t quite as simple as Sears hopping a flight to Vancouver to film with Grant Gustin and Co. for a few days.
Considering that Zoom is currently dead and unlikely to return as a regular character, perhaps Fox could do the same for Teddy Sears and let him drop back in on The Flash.
For the time being, Fox would need to lend Sears to The CW if a Zoom return were to happen.
Judging by his reveal to TV Guide, Sears is clearly game to reprise his role.