Brown sausage; drain off fat. Remove ends from zucchini. Cook whole zucchini in small amount of boiling water until crisp tender, about 8 minutes. Drain. Cut three thin slices from one zucchini; set aside. Finely chop remainder. In large bowl combine cheese and crumbs. Reserve two tablespoons and set aside. Toss remaining crumbs with sausage, chopped zucchini, chicken, parsley, salt and pepper. Beat egg whites until peaks form. Beat egg yolks and milk till blended. Stir into chicken mixture and fold into egg whites. Turn into 8x1 1/2 inch round baking dish. Combine crumbs and butter and sprinkle over top. Top with paprika. Bake uncovered at 325 degrees until set, 35-40 minutes. Garnish with reserved zucchini slices.