Preheat oven to 400 degrees F (200 degrees C). Grease a 9x13-inch baking pan with avocado oil.
Melt butter in a skillet over medium heat, about 2 minutes. Stir in garlic.
Cut zucchini into noodle shapes with a spiralizer.
Combine zucchini noodles, broccoli, mushrooms, bell peppers, and half of the basil leaves in a large bowl. Stir in butter mixture until well combined.
Pour vegetable mixture into the prepared baking pan; layer on tomatoes. Top with tomato sauce, oregano, salt, and pepper. Arrange remaining basil leaves in the pan; layer on mozzarella cheese. Cover with aluminum foil.
Bake in the preheated oven until cheese is just melted, 20 to 30 minutes. Remove aluminum foil with an oven mitt or heatproof gloves. Continue baking until vegetables are tender and cheese is bubbly, 15 to 30 minutes more.
