Preheat the oven to 350°F. Line a 9 x 9″ pan with a piece of aluminum foil.
Stir together the sugar and oil with a spatula. Then stir in the zucchini, vanilla, cocoa powder, Dutch process cocoa powder, cornstarch, flour, baking soda, and salt. Fold in 3/4 of the chocolate chips. Allow the batter to stand for 5 minutes to allow it to thicken.
Pour the batter into the pan and top with the remaining 1/4 cup chocolate chips. Bake 30 to 35 minutes until a tester comes out with a few clinging crumbs. Cool for 1 hour in the pan, then remove the brownies from the pan with the foil and allow to cool on a baking rack for another 1 to 2 hours until cooled. Slice into 16 pieces and serve (wash the knife after each slice to make for clean cuts). Leftovers store up to 1 week refrigerated.