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

In a large skillet, heat the olive oil over medium heat. Add the chopped onion, garlic, and red bell pepper. Sauté for 3-4 minutes until the vegetables begin to soften. Add the sliced zucchini and cherry tomatoes, and cook for another 5 minutes, stirring occasionally.

In a separate bowl, combine the shredded cheddar cheese, grated Parmesan cheese, sour cream, mayonnaise, dried oregano, dried basil, salt, and pepper. Mix well until all the ingredients are fully incorporated.

Spread the sautéed vegetables evenly in the prepared baking dish. Pour the cheese mixture over the vegetables and spread it out evenly. Sprinkle the breadcrumbs on top for a crispy finish.

Place the casserole in the preheated oven and bake for 25-30 minutes, or until the top is golden brown and the casserole is bubbly. Remove from the oven and let it cool for a few minutes before serving.