1. Heat 1 tablespoon of water in a large frying pan or soup pot over medium-high heat. When the water starts to sputter, add the onion and bell pepper, and cook, stirring, for about 5 minutes. Reduce the heat to medium, and add the garlic, chili powder, oregano, and basil, and cook for 2 minutes more, adding a little water as needed to prevent sticking.
2. Stir in the diced tomatoes, beans, zucchini, corn, greens, and the 4 cut-up corn tortillas, then cover and cook for 5 minutes, stirring halfway through.
3. Preheat the oven to 375°F. Set aside a 9×13-inch casserole dish (you do not need to prepare it with any oil or parchment paper).
4. Place 1 cup of the cooked vegetables into a blender, and blend until smooth (add a little water if the mixture is too thick to blend). Stir this back into the cooked vegetables.
5. Spoon the mixture into the casserole dish, and scatter the remaining 2 cut-up corn tortillas on the top. Bake uncovered for 15 minutes. Set aside for 5 minutes before serving.