HEAT oven to 375°F.
MIX first 4 ingredients until well blended.
PLACE 1 fish piece onto center of each of 4 large sheets heavy-duty foil; top each with 1 cup spinach and second fish piece. Top with zucchini, peppers and cream cheese mixture; fold to make packets. Place in single layer in 15x10x1-inch pan.
BAKE 15 min. or until fish flakes easily with fork. Remove from oven. Let stand 5 min.