Preheat your oven to 375°F (190°C).
Cook the ziti pasta according to package instructions until al dente. Drain and set aside.
In a large skillet, heat the olive oil over medium heat. Add the onion and garlic, sautéing until the onion is translucent.
Add the zucchini and bell peppers to the skillet, cooking until they are just tender.
Stir in the marinara sauce, oregano, basil, salt, and pepper. Let the sauce simmer for about 10 minutes.
In a large mixing bowl, combine the cooked ziti with the vegetable sauce, half of the mozzarella cheese, and half of the Parmesan cheese.
Transfer the pasta mixture into a greased 9×13-inch baking dish.
Sprinkle the remaining mozzarella and Parmesan cheese over the top.
Bake in the preheated oven for 25-30 minutes, or until the cheese is melted and golden brown.
Remove from the oven and let it cool for a few minutes. Garnish with fresh parsley or basil before serving.

Variations & Tips
For a heartier version, you can add cooked Italian sausage or ground beef to the vegetable mixture. If you prefer a spicier dish, consider adding a pinch of red pepper flakes to the sauce. For a gluten-free option, use gluten-free pasta. You can also experiment with different vegetables, such as mushrooms, spinach, or eggplant, depending on what’s in season or what you have on hand.