Preheat oven to 350°.
Combine first 3 ingredients in a Dutch oven; bring to a boil. Cover, reduce heat, and simmer 20 minutes or until tender. Drain; partially mash with a potato masher.
Combine zucchini mixture, rice, cheddar cheese, sour cream, 2 tablespoons Parmesan cheese, breadcrumbs, salt, pepper, and eggs in a bowl; stir gently. Spoon mixture into a 13 x 9-inch baking dish coated with cooking spray; sprinkle with 2 tablespoons Parmesan cheese. Bake at 350° for 30 minutes or until bubbly.
Preheat broiler. Broil 1 minute or until lightly browned.