Preheat oven to 325 degrees. Grease and flour one 11 x 17 inch sheet pan. In a large mixing bowl, cream the sugars, butter, oil, eggs, vanilla and buttermilk. Mix together the dry ingredients (flour,cinnamon, allspice, cocoa powder, soda and salt). Slowly add the dry ingredients to the creamed mixture. Stir in the grated zucchini. Pour mixture into prepared pan and sprinkle the chocolate chips of the top. Bake for 40 - 45 minutes or until a wooden pick come out clean.. Cool, dust with powdered sugar, if desired. Cut into bars when cool.