Preheat the oven to 350 degrees Fahrenheit (175 degrees Celsius).

In a bowl, combine the diced zucchini, orange pepper, yellow pepper, red pepper, panko bread crumbs, and shredded mozzarella cheese. Mix well to ensure all the ingredients are evenly combined.

Save half of the bread crumbs and cheese to use as a topping later.

Transfer the mixture into a cast iron pan or ovenproof dish, spreading it evenly.

Place the dish in the preheated oven and bake for 20 minutes.

After 20 minutes, switch the oven to the broiler setting to brown the top of the dish. Keep a close eye on it to prevent burning, as broiling can quickly brown the surface.

Once the top is nicely browned, remove the dish from the oven.