Preheat the oven to 350°F (175°C) and line a muffin tin with paper liners or grease it lightly.

In a large bowl, combine the grated zucchini and carrots. Squeeze out excess moisture with a clean kitchen towel or paper towels.

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

In a separate mixing bowl, beat together the granulated sugar, brown sugar, vegetable oil, eggs, and vanilla extract until well combined.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Fold in the grated zucchini, carrots, nuts, and raisins if using.

Divide the batter evenly among the muffin cups, filling each about ¾ full.

Bake for 18-22 minutes or until a toothpick inserted in the center comes out clean.

Allow the muffins to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.