Preheat oven to 350°F and line a 12-cup muffin tin or spray with nonstick spray.
In a large bowl, whisk the eggs, oil, sugar, and vanilla until smooth.
Stir in the grated zucchini and drained pineapple until combined.
In a separate bowl, whisk together the flour, baking soda, baking powder, cinnamon, and salt.
Add the dry ingredients to the wet mixture and stir until just combined—do not overmix.
Fold in the chopped walnuts gently.
Scoop the batter evenly into the prepared muffin tin, filling each cup about 3/4 full.
Bake for 18 to 22 minutes or until a toothpick inserted in the center comes out clean.
Let muffins cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.