1) In a mixing bowl, cream butter and sugar. Add eggs, one at a time, beating well after each addition. Beat in oil and vanilla. Combine the flour, cocoa, baking soda, baking powder and cinnamon; gradually add to the creamed mixture. Fold in zucchini and walnuts if desired.
2) Spread into a greased 13-in. x 9-in. x 2-in. baking pan. Sprinkle with chocolate chips. Bake at 350 degrees F for 30-35 minutes or until a toothpick inserted near the center comes out clean. Cool on a wire rack.