1) Preheat the oven to 325°F. Lightly grease a 9" x 13" pan.
2) In a large mixing bowl, beat together the butter, oil, sugar, vanilla, baking soda, baking powder, and salt until smooth.
3) Beat in the eggs.
4) Stir in the sour cream, buttermilk, or yogurt alternately with the flour.
5) Add the cocoa and espresso powder, mixing until smooth.
6) Fold in the zucchini and 1/2 cup chocolate chips. Spoon the batter into the prepared pan.
7) Bake the cake for 30 to 35 minutes, until the top springs back lightly when touched, and it seems set.
8) To ice the cake: Slide the cake out of the oven, sprinkle it evenly with the 1 cup chocolate chips, and return it to the oven for 5 minutes, or until a cake tester inserted in the center comes out clean.
9) Remove the cake from the oven, and use a cake spatula or rubber spatula to spread the chocolate chips into a smooth glaze. Cool on a rack.
Yield: 24 servings.