Preheat your oven to 350 F and prepare a bread pan or glass baking dish with cooking spray.
Add the all-purpose flour, whole wheat flour, baking soda, baking powder, salt, cinnamon and nutmeg to a large bowl. Add chocolate chips/walnuts/raisins, if using. Whisk to combine and set aside.
In another bowl, add the melted (and slightly cooled) butter, brown sugar, white sugar, egg/flax egg, vanilla extract, and grated zucchini. Mix until everything is combined.
Gently fold the wet ingredients into the dry ingredients with a spatula until just combined. Pour the batter in the prepared bread pan or baking dish. Bake for 50-55 minutes, until the top of the bread is golden brown and firm to the touch (and you can also insert a toothpick into the center and make sure it comes out clean!)
Let the bread cool down before slicing!