Preheat oven to 350° F. Grease and flour a 9” x 13” baking pan.
In a large bowl, combine the oil, sugar and 2 teaspoons vanilla and mix until well blended.
Combine the flour, ½ cup cocoa, baking soda, and salt and add to the sugar mixture. Fold in the zucchini and walnuts. Note: Batter will seem dry, but don’t worry! The zucchini provides moisture when baking! If you want to add water, add by tablespoonfuls but batter should be dry.
Spread the batter evenly into the pan. Bake for 25 to 30 minutes, until brownies spring back when gently touched.
To make the frosting, melt together the 6 tablespoons of cocoa and butter; set aside to cool. In a medium bowl, blend together the confectioners’ sugar, milk and ½ teaspoon vanilla. Stir in the cocoa mixture.
Spread over cooled brownies before cutting into squares.