Our general rules for bracketing are as follows: 1. Engage the bracket. If no one cuts, the defense wins. 2. Overload the bracket. This is usually one cutter making a hard cut to the most dangerous spot, usually near where the bracket is setup. The 2nd cutter follows on their heels, reads the situation and takes the available throw. Usually a slightly more difficult throw (slight break), but to an uncovered receiver 3. Moving the disc is good, but only after the bracket has been engaged. If no cuts happen and the disc just moves, it's usually just into another bracket.
From this position, we're going to have a fixed set of cuts to get our offense going. The goal is to overload the open side under defender with two cuts, forcing them to make choices, and ideally to break the bracket immediately.
The '3' cutter attacks the open side first, dragging the under defender out of position. The '2' cutter then follows into the under space.
When we hit the under, the defense is then left scrambling. The '3' cutter, who didn't get the disc, should force the under defender to either commit to them or the mark. If that defender tries to deny the cutter, the deep defender must then come down to mark, leaving deep space for the 1 and 4 cutters to attack.