1. Heat oven to 325 degrees F. Coat 13 x 9 x 2-inch baking pan with nonstick cooking spray.
2. In a large bowl, whisk together flour, cocoa powder, baking soda, cinnamon and baking powder. Set aside.
3. In another large bowl, beat shortening, oil, sugar and egg on low speed until smooth. Beat in sour cream and vanilla, then flour mixture. Beat on medium for 2 minutes. Fold in zucchini and chocolate.
4. Spread into prepared pan. Sprinkle nuts on top. Bake at 325 degrees F for 30 to 35 minutes or until a toothpick inserted in center comes out clean. Cool in pan on wire rack. To serve, cut into 16 bars.