Preheat the oven to 325°F. Lighlty grease a 9" x 13" pan.
In a large mixing bowl, cream together the butter, oil, sugar, vanilla, baking soda, baking powder, and salt. Beat in the eggs.
Stir in the sour cream, buttermilk, or yogurt alternately with the flour. Then add the cocoa and espresso powder, mixing till smooth. Finally, fold in the zucchini and 1/2 cup chocolate chips.
Spoon the batter into the prepared pan. Bake the cake for 30 to 35 minutes, till the top springs back lightly when touched, and it seems set. Slide the cake out of the oven, sprinkle it evenly with the 1 cup chocolate chips, and return it to the oven for