Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners or grease it lightly.
In a large bowl, combine the grated zucchini, crushed pineapple, and chopped walnuts. Mix well and set aside.
In another bowl, whisk together the all-purpose flour, granulated sugar, brown sugar, baking soda, baking powder, salt, cinnamon, and nutmeg.
In a separate bowl, beat the eggs, then add the vegetable oil and vanilla extract. Mix until well combined.
Pour the wet ingredients into the dry ingredients and stir until just combined. Gently fold in the zucchini, pineapple, and walnuts until evenly distributed.
Divide the batter evenly among the muffin cups, filling each about two-thirds full.
Bake in the preheated oven for 20-25 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Allow the muffins to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.