Preheat the oven to 375°F (190°C). Slice the zucchini and place it in a colander to drain excess moisture.

After 10 minutes, pat the zucchini dry with paper towels.

In a skillet over medium heat, sauté the bell pepper and onion until softened, about 5 minutes.

In a mixing bowl, combine the drained zucchini, sautéed vegetables, cooked sausage, pizza sauce, Italian seasoning, salt, and pepper.

Spread half of the zucchini mixture in a greased casserole dish. Top with half of the mozzarella cheese.

Repeat with the remaining zucchini mixture and mozzarella cheese, then sprinkle the Parmesan cheese on top.

Bake in the preheated oven for 25-30 minutes, or until the cheese is bubbly and golden brown.

Let the casserole cool for a few minutes before slicing and serving.