Forcing middle. Sets up in regular zone with D1-3 as the cup, D4 and D6 as the wings, D5 as the short deep, and D7 as the deep deep. The cup is focused on stopping upfield throws and forcing swing passes. D5 plays the gaps and talks to the cup.
As the disc gets swung from one sideline to the other, the mark and force changes. With a swung disc, the wing defender on that side needs to guard the offensive wing to prevent the continue throw and let the cup catch up.
After a set number of throws, the defense can transition to a clam defense. The cup simply picks up the handlers.
The transition can also be to a man defense.