Preheat the oven to 350°F (175°C). Grease and flour a 9x5-inch loaf pan or line it with parchment paper for easy removal.
Grate the zucchini using a box grater or food processor. Squeeze out any excess moisture from the zucchini using a clean kitchen towel or paper towels. In a large mixing bowl, combine the flour, baking powder, baking soda, cinnamon, nutmeg, cloves, and salt. Mix well to combine.
In another bowl, whisk together the sugar, oil, eggs, and vanilla extract until smooth and well-combined.
Add the grated zucchini to the wet ingredients and stir to combine.
Gradually add the wet ingredients into the dry ingredients, mixing gently just until combined. If using, fold in the walnuts or chocolate chips. Pour the batter into the prepared loaf pan and spread it evenly.
Bake for 60-70 minutes, or until a toothpick inserted into the center comes out clean or with just a few moist crumbs.
Cool the bread in the pan for about 10 minutes, then transfer it to a wire rack to cool completely before slicing.