Zucchini Brownies

3/4 cup vegetable oil
2 cups white sugar
2 teaspoons vanilla extract
2 cups all-purpose flour
1/2 cup cocoa powder
1 1/2 teaspoons baking soda
1 teaspoon salt
2 cups shredded zucchini
1/2 cup chopped walnuts

6 tablespoons unsweetened cocoa powder
1/4 cup margarine
2 cups confectioners' sugar
1/4 cup milk
1/2 teaspoon vanilla extract

1. Preheat oven to 350 degrees F. Grease and flour a 9x13 inch baking pan.
2. In a large bowl, mix together the oil, sugar and 2 teaspoons vanilla until well blended. Combine the flour, 1/2 cup cocoa, baking soda and salt; stir into the sugar mixture. Fold in the zucchini and walnuts. Spread evenly into the prepared pan.
3. Bake for 25 to 30 minutes in the preheated oven, until a tooth pick comes out clean.
4.  To make the frosting, melt together the 6 tablespoons of cocoa and margarine; set aside to cool. In a medium bowl, blend together the confectioners' sugar, milk and 1/2 teaspoon vanilla. Stir in the cocoa mixture. Spread over cooled brownies before cutting into squares.