Preheat your oven to 350°F (175°C). Grease a 9×5-inch loaf pan with nonstick spray or a thin layer of oil. For easy removal, line the pan with a strip of parchment paper that overhangs the long sides like a sling.
Wash and dry the zucchini. Grate it on the medium holes of a box grater until you have about 1 1/2 cups lightly packed. Gather the grated zucchini in your hands and gently squeeze over the sink to remove excess water, but do not wring it completely dry. Set aside.
In a medium bowl, whisk together the flour, baking soda, baking powder, salt, cinnamon, and nutmeg (if using) until evenly combined with no visible streaks of spice.
In a large mixing bowl, whisk together the sugar and oil for about 30 seconds until smooth and slightly glossy. Add the eggs and vanilla, then whisk again until the mixture is thickened slightly and well combined.
Stir the grated zucchini into the wet mixture using a spatula or wooden spoon until evenly distributed. The mixture will look loose; that is expected.
Add the dry ingredients to the wet ingredients in two additions. Gently fold with a spatula, turning the bowl as you go, just until you no longer see streaks of flour. If using nuts or chocolate chips, sprinkle them over the batter during the last few folds so they are evenly distributed. Do not overmix; a few small flour streaks will disappear as it bakes.
Pour the batter into the prepared loaf pan and smooth the top with a spatula. If desired, sprinkle 1–2 tablespoons of coarse sugar evenly over the surface for a crunchy, sparkly crust.
Place the pan on the center rack of the preheated oven. Bake for 50–60 minutes, or until the top is deep golden brown and a toothpick inserted in the center comes out mostly clean with just a few moist crumbs (not wet batter). If the top is browning too quickly while the center is still not done, tent the loaf loosely with foil for the last 10–15 minutes of baking.
Let the zucchini bread cool in the pan for 10–15 minutes. Then use the parchment sling (or carefully invert) to remove the loaf and transfer it to a wire rack. Allow it to cool completely for at least 1 hour before slicing for the best texture and flavor.
Once cooled, slice the zucchini bread with a serrated knife. Serve plain, or with softened butter, cream cheese, or a drizzle of honey. The flavor and texture are even better the next day.