Preheat oven to 400°. Place zucchini on towels and in a colander or bowl. Let stand 10 minutes, then squeeze out moisture.
Combine zucchini with eggs, Parmesan and half of mozzarella and cheddar cheeses. Press into a greased 13x9-in. or 3-qt. baking dish. Bake 20 minutes.
Meanwhile, in a large saucepan, cook beef and onion over medium heat, crumbling beef, until meat is no longer pink; drain. Mix in taco seasoning. Add tomato sauce; spoon over zucchini mixture. Sprinkle with remaining cheeses; add red pepper. Bake until heated through, about 20 minutes longer.
Freeze option: Cool baked casserole; cover and freeze. To use, partially thaw in refrigerator overnight. Remove from refrigerator 30 minutes before baking. Preheat oven to 350°. Unwrap casserole; reheat on a lower oven rack until heated through and a thermometer inserted in center reads 165°. Yield: 8 servings.
Can freeze in single servings, need to defrost half power before toster oven or the microwave