Preheat oven to 350°. Grease two 8x4-in. loaf pans. In a large bowl, beat sugar, oil, eggs and vanilla until well blended. In another bowl, whisk flour, salt, baking soda, lemon zest, cinnamon and baking powder; gradually beat into sugar mixture, mixing just until moistened. Stir in zucchini and walnuts.
Transfer to prepared pans. Bake 55-65 minutes or until a toothpick inserted in center comes out clean. Cool 10 minutes before removing from pans to wire racks to cool.