4-3W-3 or 3W-4-3
His defense has two points of vulnerability. The flanks and the middle of the backline. This can be exploited with a ML and MR in addition to three strikers. The 3W defenders especially is extremely weak and should never holdup against 3 strikers.
Attacking, down both flanks, whole pitch pressing, short passing, hard tackling, no counter. Red arrows on DL, DR, ML and MR.
4-4-2 classic might work as well, if you don't want to use an attacking mentality.