In a large bowl, whisk eggs, sugar, and vanilla extract together.
Stir in grated zucchini and melted butter.
In a separate bowl, combine the dry ingredients (flour, baking soda, baking powder, salt, and cinnamon).
Fold the dry ingredients into the wet zucchini mixture.
Add in the chocolate chips and walnuts (optional). Stir to combine.
Line muffin pan with paper liners. Fill each mold to the top with batter.
Bake at 350°F for 30 minutes, or until a toothpick inserted into the center of each muffin comes out clean and the outside is golden brown. Let muffins cool for 5 minutes. Enjoy!