My guess is something else is airborne that's requiring multiple air refuelings. The fact they're the second one doing this and the call sign ZOMBI tells me they're just burning holes in the sky.
Which could mean there are some pilots who need to maintain currency and are about to run out of fiscal year funds. Which would mean they have several pilots on board and are trading out left seat/ right seat to get in the requisite number of orbits. Hence zombies and the long boring hours of burning holes in the sky.