Preheat your oven to 375°F (190°C) and grease a 9x13 inch baking dish with cooking spray or olive oil.

In a large skillet, heat olive oil over medium heat. Add the diced onion and sauté for about 5 minutes.

Stir in the minced garlic, diced red bell pepper, and zucchini. Cook for another 5 minutes.

Add corn kernels, black beans, chili powder, ground cumin, salt, and pepper to the skillet. Cook for 2 additional minutes.

In the greased baking dish, spread a layer of enchilada sauce evenly across the bottom.

Layer 3-4 corn tortillas over the sauce, add half of the vegetable mixture, followed by 1/3 of the shredded cheese.

Repeat with another set of tortillas, the remaining vegetable mixture, and another 1/3 of the cheese, pouring ½ cup of enchilada sauce over this layer.

Top with remaining tortillas, last of the enchilada sauce, and final 1/3 of shredded cheese.

Cover the baking dish with foil and bake for 20 minutes.

After 20 minutes, remove the foil and bake for an additional 10 minutes or until the cheese is golden and bubbly.

Let the casserole rest for 5 minutes to set before slicing.

Sprinkle freshly chopped cilantro on top before serving.

Serve with optional toppings like avocado or sour cream.