Preheat your oven to 350˚F and grease two 8×4-inch loaf pans.
In a medium bowl, whisk together the flour, sugar, baking powder, baking soda, cinnamon, and salt. Set aside.
In a large bowl, add the grated zucchini, oil, eggs, and vanilla. Mix well to combine.
Add the dry ingredients and walnuts to the zucchini mixture. Gently fold until JUST combined. Do not overmix.
Divide the batter between two loaf pans and bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean. I like to cover them with aluminum foil after 30 minutes so that the tops do not get too dark.
Let the bread cool in the pan(s) for 15 minutes before transferring them to a wire rack to cool completely.