Preheat oven to 350°F (175°C). Grease a 9x5-inch loaf pan or line with parchment paper.
In a large bowl, whisk together flour, baking soda, baking powder, salt, cinnamon, and nutmeg.
In another bowl, beat eggs, sugars, oil, and vanilla until smooth.
Stir wet ingredients into dry mixture, then fold in zucchini and optional mix-ins.
Pour batter into the prepared pan and smooth the top.
Bake for 50–60 minutes, or until a toothpick inserted in the center comes out clean.
Let cool in the pan for 10 minutes before transferring to a wire rack.