Preheat oven to 400 degrees. Add oil and onion to a hot skillet and stir. Add zucchini and red pepper. Saute until tender. Season with cumin, cayenne and salt. Add thawed frozen corn and mix together. Place 2 tortillas on cookie sheet. Sprinkle with grated cheese and a large spoonful of veggie mixture. Top with a second tortilla, cheese, and mixture. Top with third tortilla. Bake until cheese is melted, about 5 to 8 minutes. Cut into quarters and serve bubbling hot.