Preheat oven to 350 degrees. Cut zucchini into chunks - set aside. Remove and discard sausage casings, break up the meat and saute in a 10" skillet over moderate heat for 5 minutes. Add the onion, basil,marjoram and zucchini. Cook 5 minutes more. Remove from heat, add bread crumbs, 2 tablespoons of the Parmesan cheese and the salt and pepper. Mix the egg with the stuffing mixture and place in a buttered casserole dish. Sprinkle remaining 2 tablespoons Parmesan cheese on top. Bake, uncovered for 35 to 45 minutes or until heated thoroughly and the casserole has a lightly brown crust.