Preheat oven to 350 degrees. Spray a 12 cup bundt pan with nonstick baking spray.
Beat the butter and sugars until creamy. Add the eggs and vanilla and beat again.
Whisk together the flour, cocoa powder, baking powder, baking soda, salt, cinnamon, and nutmeg.
Add the dry ingredients alternately with the buttermilk until everything is incorporated. Mix in the zucchini and chocolate chips by hand, or on low speed of mixer.
Pour batter into prepared Bundt pan. Bake for 45-55 minutes, or until a toothpick inserted into the center of the cake comes out mostly clean. Remove from oven, and cool in the pan for 15 minutes, then flip it out onto a plate and cool completely.