In a large skillet over medium heat, add the olive oil. Once hot, toss in the diced zucchini, sliced green onions, diced green pepper, and sliced green olives. Sauté for about 5 minutes, or until the vegetables are tender. Add the chopped spinach, cumin, salt, and pepper, and cook for an additional 2 minutes until the spinach is wilted.
In a mixing bowl, combine the cooked, shredded rotisserie chicken, rinsed black beans, and salsa. Mix well until everything is evenly coated.
Preheat your oven to 350°F (175°C). In a 9x13 inch casserole dish, spread a thin layer of the green enchilada sauce on the bottom. Layer 3 slices of corn tortillas over the sauce. Next, add half of the chicken and bean mixture, followed by half of the sautéed vegetables. Sprinkle with half of the grated cheddar cheese. Repeat the layers, finishing with the remaining cheddar cheese on top.
Pour the remaining green enchilada sauce over the top layer of cheese. Cover the casserole with aluminum foil and bake in the preheated oven for 25 minutes. Then, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Once baked, remove the casserole from the oven and let it cool for a few minutes. Garnish with chopped cilantro and your favorite toppings such as sour cream, diced tomatoes, avocado, lettuce, and a squeeze of lime juice. Serve warm and enjoy!