Preheat the oven to 350°F
Put the zucchini in a food processor and blend well. It should be like a very thick juice at this point. You don't want any large pieces.
In a large bowl, stir together the zucchini, butter, eggs, vanilla, and sugars until just blended.
In another bowl, whisk together the cocoa, baking powder, salt, and flour. Stir the dry ingredients in with the wet ingredients until combined. Fold in the chocolate chips.
Pour the batter into an 8-inch square baking pan lined with parchment paper. Top with nuts or candies if using. Bake for 20-25 minutes.