Preheat your oven to 350°F. Lightly grease a 9" square pan., To make the brownies: Combine the zucchini, melted butter, eggs, and vanilla in the work bowl of a food processor, and process until smooth., Add the sugar, cocoa powder, espresso powder, baking powder, salt, and flour; process briefly, just until well combined., Add the chips, and pulse several times, to break up the chips just a bit., Pour the batter into the prepared pan., Bake the brownies for 25 to 30 minutes, until a toothpick inserted into the center comes out clean, or with a few moist crumbs clinging to it; you shouldn't see any sign of wet batter. Remove the brownies from the oven, and allow them to cool completely before frosting., To make the frosting: Combine the chocolate chips and milk or cream in a microwave-safe bowl or small saucepan. Heat until the milk is steaming, and the chips are soft. Remove from the heat, and stir until smooth., Spread the frosting atop the brownies. Place them in the refrigerator for an hour or so, to set; then store them at room temperature, covered, for several days.