Preheat oven to 325. Grease and flour a 9x13 inch baking pan.
Sift the flour, cocoa powder, baking soda & salt into a medium bowl.
In another bowl, beat the sugar, butter and oil in a large bowl until well blended. Add the eggs 1 at a time, beating well after each addition. Add the vanilla extract.
Mix in the dry ingredients alternating with the buttermilk in 3 additions. Mix in grated zucchini.
Spread into prepared pan (I used an offset spatula for even spreading). Sprinkle with chocolate chips. Bake 50 minutes or until toothpick inserted into the center comes out clean. Allow to cool about 15 minutes, slice, and serve warm.