This photo pass of the six-ship Delta is the first maneuver while in the formation. Getting a photo of it isn't really that difficult. One of the reasons is the fact that you're trying to get all six F-16s in the frame of the camera; this results in a bigger target. Also, you're not zooming in as much; so tracking the formation will be easier.

Even so, not all photos will come out cleanly; sometimes you have to take multiple shots to get the results you want!