The 3-3-1 zone involves a 3 person cup that chases the disc. 3 mid field players. And a single defender deep. (Red is on defense.)
Typically the cup tries to force the disc to one of the sidelines based on the wind. The positions in the cup remain the same regardless of where the disc is on the field, unless a call is made to switch or trap.
The mid-mid (#5) stops any throw between the top of the cup (#2 and #3).
The mark (#1) in the cup stops the flat throw to the break side. Primarily, the back hand around, but also the flat I/0 forehand.
The top (#2) of the cup, stops the breakside down field throw between them and the mark.
The chase (#3) of the cup, stops the force side down field throw. Only flat throws to the side line are permitted.
The wings (#4 and #6) stop the down field continuation.
The deep (moster, #7) stops the deep threat. Primarily shading to the force side of the field.
If the disc is swung to the side line.
It is important for the breakside wing (#4) to expect to help the deep by taking away the break-side hammer.