Preheat the oven to 400°F and grease a 12-cup muffin tin or line it with paper liners.

In a medium bowl, whisk together the flour, baking powder, cinnamon, baking soda, nutmeg, and salt.

In a large bowl, whisk together the sugar, vegetable oil, eggs, milk, and vanilla. Stir in the zucchini.

Add the dry ingredients to the wet ingredients and mix until just combined. Fold in the walnuts.

Evenly divide the batter among the prepared muffin cups, adding about a scant 1/3 cup to each one. Bake for 15 to 20 minutes, or until the tops spring back to the touch and a toothpick inserted comes out clean.

Allow the muffins to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.