Preheat oven to 350°F (175°C) and grease a 9×5-inch loaf pan or line it with parchment paper.
Grate the zucchini and lightly squeeze out excess moisture—leave it slightly damp.
Whisk together the flour, baking soda, baking powder, salt, cinnamon, and nutmeg.
In another bowl, whisk sugar, eggs, sour cream, oil, and vanilla until smooth.
Stir in the zucchini until evenly mixed.
Add the dry mixture to the wet ingredients and stir gently until just combined.
Fold in chocolate chips, nuts, coconut, or lemon zest if using.
Pour the batter into the pan, smooth the top, and bake for 50–65 minutes, until a toothpick comes out clean.
Cool for 10 minutes in the pan, then transfer to a wire rack to cool completely.