Grease and flour a 13x9x2-inch baking pan; set aside. In a large bowl, beat together eggs, granulated sugar, cooking oil, and cream with an electric mixer on low speed. Add zucchini and beat until mixed.
In another bowl, combine the flour, the 1/4 cup cocoa powder, the baking powder, baking soda, ground cinnamon, and salt. Gradually beat flour mixture into egg mixture. Stir in the nuts.
Turn batter into prepared pan. Bake in a 325 degree F oven for 60 to 70 minutes or until the cake tests done. Let the cake cool in the pan on a wire rack.
Frost cooled cake with Cream Cheese Frosting. Sprinkle frosted cake with additional cocoa powder, if you like. Cut the cake into squares to serve. Makes 12 to 24 servings.
In a small bowl, beat together cream cheese, butter, and vanilla. Beat in powdered sugar to make a frosting consistency. Makes 1-1/2 cups.