Preheat your oven to 350°F (175°C).
Prepare the zucchini by grating it and squeezing out excess moisture.
In a bowl, combine the grated zucchini, cheddar cheese, mozzarella cheese, Parmesan cheese, eggs, garlic powder, onion powder, salt, and pepper.
Transfer the mixture to a greased 9x13 inch baking dish, spreading it out evenly.
Sprinkle breadcrumbs evenly over the top of the casserole.
Bake in the preheated oven for 30-35 minutes or until the top is golden and bubbly.
Remove from the oven and let it cool for a few minutes before slicing.