Combine oil, sugar, and eggs in a large mixing bowl; beat at medium speed until well blended.
In another bowl, combine the flour and next 5 ingredients; stir well. Add the flour mixture to the creamed mixture, beating until well blended. Stir in zucchini.
Pour the batter into an ungreased 15 x 10 x 1 inch jellyroll pan. Bake at 350 degrees for 25 minutes or until a wooden pick inserted in the center comes out clean. Let cool in the pan on a wire rack. Once cool, spread cream cheese frosting evenly over the top; cut into bars.
Combine the cream cheese, butter, and vanilla in a small mixing bowl; beat at medium speed until light and fluffy. Add the powdered sugar, beating until the frosting is smooth. Spread on the cooled zucchini bars.