In a large bowl, combine sugar and oil. Add eggs, one at a time, beating well after each addition. Combine flour, cocoa, baking soda, baking powder and salt; gradually add to the egg mixture alternately with the milk. Stir in the zucchini and extract. Pour into a greased 15x10x1-in. baking pan. Bake at 375° for 25 minutes or until cake tests done. While cake is baking, combine all frosting ingredients. Mix until smooth. Spread frosting over cake while hot. Cool on wire rack.