Preheat your oven to 400°F (200°C).

Toss the shredded zucchini with 1/2 teaspoon of salt and let it sit for 10 minutes.

Squeeze out the excess moisture from the zucchini using a clean kitchen towel.

In a mixing bowl, combine the drained zucchini with 2 large eggs, 1/2 cup grated Parmesan cheese, and 1 cup shredded mozzarella cheese, stirring until well incorporated.

Grease a 9x13-inch baking dish and pour the zucchini mixture in, pressing it down evenly to create a crust.

Bake the crust in the preheated oven for 20 minutes until lightly browned.

In a skillet, heat over medium heat and cook 1 pound of ground beef with 1/2 cup chopped onion until browned.

Drain excess fat, then stir in 2 cups of pizza sauce, 1 chopped green bell pepper, 1/2 cup sliced mushrooms, 1/2 teaspoon dried oregano, 1/2 teaspoon garlic powder, and 1/4 teaspoon black pepper. Let simmer for 5 minutes.

Spread the beef and vegetable mixture evenly over the baked crust.

Sprinkle the remaining 1 cup of mozzarella cheese and all of the cheddar cheese over the meat mixture.

Bake the assembled casserole for an additional 20 minutes until cheese is melted and golden brown.

Let cool for a few minutes before slicing into squares and serve warm.