Prep the pan and oven: Preheat your oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line it with a parchment sling for easy removal.
Grate the zucchini: Use the large holes of a box grater.
Gather the grated zucchini in a clean kitchen towel and gently squeeze out excess moisture. Don’t wring it dry—just remove the drips.
Mix the dry ingredients: In a large bowl, whisk together the all-purpose flour, whole wheat flour, cinnamon, nutmeg, baking soda, baking powder, and salt until well combined.
Whisk the wet ingredients: In a separate bowl, whisk the eggs, granulated sugar, brown sugar, oil, yogurt (or sour cream), and vanilla until smooth and slightly thickened.
Combine wet and dry: Pour the wet mixture into the dry ingredients. Stir gently with a spatula until a few flour streaks remain.
Don’t overmix.
Fold in zucchini and add-ins: Add the grated zucchini and any optional nuts or chips. Fold just until evenly distributed and no dry spots remain.
Fill the pan: Scrape the batter into the prepared pan and smooth the top. If you like, sprinkle a spoonful of turbinado sugar on top for a light crunch.
Bake: Bake for 55–65 minutes, or until a toothpick inserted in the center comes out clean or with a few moist crumbs.
If the top browns too quickly, tent loosely with foil for the last 10–15 minutes.
Cool: Let the bread cool in the pan for 10–15 minutes. Lift it out and cool completely on a wire rack before slicing. This helps set the crumb and keeps slices neat.
Slice and serve: Use a serrated knife for clean slices.
Enjoy warm or at room temperature with butter, cream cheese, or plain.