Place a large round or rectangular baking sheet (I used a round stone) in the oven and preheat oven to 450°F.
Add zucchini, eggs, flour, 1/4 cup shredded mozzarella cheese, Parmesan cheese, onion powder, pizza seasoning, garlic powder, and salt to a food processor and chop until all of the ingredients are finely chopped and well combined.
With pot holders, remove the baking sheet from the oven. Carefully place parchment paper over the heated baking sheet. Using a spatula, spread the zucchini mixture into a circle about 9-10 inches wide onto the parchment paper.
Bake zucchini crust for 15 minutes. Using a large spatula, carefully flip the crust and bake an additional 10 minutes.
Scoop spaghetti sauce onto the zucchini crust and spread with the back of a spoon. Top with the extra 1/2 cup shredded mozzarella cheese and slices of turkey pepperoni. Place back in the oven and allow to cook 3-5 more minutes, or until the cheese is melted.
Using the big spatula, transfer the pizza to a large cutting board. Using a pizza cutter or knife, slice pizza into 8 equal slices.