01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with olive oil or nonstick spray.
02 - Heat olive oil in a large skillet over medium heat. Add diced onion and bell pepper and sauté for 3 to 4 minutes until softened.
03 - Add ground beef to the skillet and cook, breaking up with a spoon, until browned and fully cooked for 5 to 6 minutes. Drain excess fat if necessary.
04 - Stir in garlic, zucchini, corn kernels, and black beans. Cook for 3 to 4 minutes until vegetables are nearly tender.
05 - Sprinkle cumin, chili powder, smoked paprika, salt, and black pepper into the skillet and stir to combine evenly.
06 - Spread 1/2 cup enchilada sauce evenly on the bottom of the prepared baking dish.
07 - Arrange half of the tortilla quarters over the sauce. Spoon half of the beef-vegetable mixture over the tortillas, top with 2/3 cup of cheese, then pour 3/4 cup enchilada sauce over the cheese.
08 - Repeat layers with remaining tortillas, beef-vegetable mixture, 2/3 cup cheese, and remaining enchilada sauce.
09 - Sprinkle remaining cheese evenly across the surface.
10 - Bake uncovered for 25 to 30 minutes until casserole is bubbling and the cheese is melted and golden.
11 - Allow casserole to rest for 5 to 10 minutes before slicing and serving. Garnish with cilantro, green onions, or avocado as desired.