Sift flour, cocoa, salt, soda, and baking powder together. Set aside. Cream butter, oil, and sugar in mixing bowl using electric mixer on medium speed. Beat until light and fluffy. Beat eggs into creamed mixture one at a time, beating well after each addition. Blend vanilla into creamed mixture. Add dry ingredients alternately with milk beating well after each addition. Stir in zucchini. Pour into lightly greased
9 x 13 pan. Sprinkle with chocolate pieces and chopped walnuts. Bake at 325 to 350 degrees for 40 to 55 minutes until done.