Preheat oven to 350 degrees.
Heat oil in skillet. Add zucchini and onion and cook 5 minutes or until golden brown and tender. Add spinach and corn. Cook and stir until spinach wilts.
Spread 1/2 cup enchilada sauce in 3-quart shallow baking dish. Place 6 tortillas, overlapping as needed to cover bottom of dish. Spread with half of remaining enchilada sauce. Top with vegetable mixture and half the cheese. Top with remaining tortillas and enchilada sauce.
Bake 20 minutes. Top with remaining cheese and bake 5 minutes or until cheese melts. Cut into 6 squares and garnish with cilantro.