Preheat oven to 400°F. Lightly coat a 9-by-13-inch baking pan with cooking spray.
Lay quartered tortillas in a single layer on a cookie sheet. Lightly brush with oil. Bake in oven 3-5 minutes, enough to soften and very slightly crisp the edges.
Cook hamburger until pink is gone. Add onion and cook, stirring often, until it starts to brown, about 5 minutes. Drain grease. Stir in zucchini, beans, tomatoes, corn, cumin, chili powder, and salt and cook, stirring occasionally, until the vegetables are heated through, about 3 minutes.
Scatter half the tortilla pieces in the pan. Top with half the vegetable mixture, half the enchilada sauce and half the cheese. Repeat with one more layer of tortillas, vegetables, sauce and cheese. Cover with foil.
Bake the casserole for 15 minutes. Remove the foil and continue baking until the casserole is bubbling around the edges and the cheese is melted, about 10minutes more.