Preheat oven to 375° F. Grease or line 12 standard muffin cups.
In a medium mixing bowl, whisk together the gluten free flour, baking soda, baking powder, cinnamon, salt, and nutmeg. Set aside.
In a large mixing bowl, stir together the melted butter, sugars, eggs, and vanilla until combined. Add the zucchini and stir to combine.
Add the dry ingredients to the wet ingredients and stir until combined.
Divide the batter among the prepared muffin cups, using about 3 tablespoons of batter per cup.
Bake for 18-20 minutes or until a wooden pick inserted into the center of a muffin comes out clean.
Cool the muffins in the pan for 5 minutes. Then transfer the muffins to a wire rack to cool completely.
Check the ingredients of your gluten free flour mix for xanthan gum. If your flour mix doesn’t contain it, try adding ½ teaspoon to the recipe.
Lining your muffin pan with baking cups works better than greasing the pan. The baking cups help the muffins keep their shape when you remove them from the pan. The baking cups also make storing and transporting the muffins easier.
When adding the dry ingredients to the wet ingredients, be careful not to overmix the batter. Overmixing can lead to muffins that are tough.