Preheat the oven to 350°F and line a 9x13" pan with foil and baking spray.
Combine the oil, sugar and vanilla with an electric mixer until well blended. Add the flour, cocoa powder, baking soda and salt. The batter will be very dry. Then, fold in the zucchini. Fold in the chocolate chunks. I alway save some for sprinkling on top when the brownies are done baking.
Pour the batter into the pan and bake for about 30 minutes. The brownies are done when a toothpick inserted into the middle comes out with few crumbs.
This recipe is adapted from I Am Baker.