Quickly jump up to the right-most double-width platform on the second row up, just below the Zen-Chan on the right. When the monsters start moving, you should be able to trap two Zen-Chan and a Mighta together and burst them as a group. Then head to the bottom/left of the level and group together another two Zen-Chan and Mighta. The last Mighta can then be taken out alone.