Place sugars, cream cheese, and vegetable oil in a large bowl, and beat with a mixer at medium speed until well blended. Add eggs and vanilla.
Combine 2 1/2 cups flour, 1/2 cup of cocoa, baking powder, baking soda, salt, and cinnamon in a medium bowl, stirring well with a whisk.
Add flour mixture and buttermilk. Stir in zucchini, and 2/3 cup chocolate chips. Pour batter into prepared pan. Bake for 1 hour or until a wooden pick inserted in cake comes out clean. Cool in pan 10 minutes on a wire rack; remove from pan. Cool completely on wire rack.
Then add your favorite frosting or glaze on top.
Whip the butter on medium-high speed for 5 minutes, stopping to scrape the bowl once or twice.
Reduce the speed to low and gradually add the powdered sugar. Once all of the powdered sugar is incorporated, increase the speed to medium-high and add the vanilla and milk, mixing until incorporated. Mix on medium speed until light and fluffy, scraping the bowl as needed.
If frosting is too thick add a little more milk, or add more powdered sugar if not thick enough.
The recipe calls for this cake to be baked in a bundt pan, however, not everyone has a bundt pan. This recipe could easily by made in a 9×9 inch or 9×13 inch pan, and taste just as good.