Preheat the oven to 350°F (175°C) and lightly spray a 9x9-inch baking dish with nonstick spray.
Heat the olive oil in a large skillet over medium heat.
Sauté the diced zucchini, sliced green onions, and diced green pepper until they begin to soften, about 5 minutes.
Add the sliced olives, chopped spinach, cumin, and salt and pepper; cook, stirring, until the spinach wilts.
Remove the skillet from heat and stir in the chopped rotisserie chicken, black beans, salsa, and chopped cilantro to make the filling.
Spread 1/4 cup of enchilada sauce across the bottom of the prepared baking dish.
Place a layer of tortilla strips over the sauce, then sprinkle with some grated cheddar.
Spread half of the chicken and vegetable filling over the tortillas and cheese, then add more cheese, another layer of tortilla strips, and 3/4 cup enchilada sauce.
Add another layer of cheese, the remaining half of the filling, more cheese, the last tortilla strips, 1 cup enchilada sauce, and finish with the remaining cheese.
Cover the dish and bake at 350°F for 30–45 minutes, until heated through and cheese is melted.
Remove from the oven and let the casserole rest 10 minutes before cutting and serving; top with desired toppings.