Preheat your oven to 350°F (175°C).
Grease your muffin tin with cooking spray or line each cup with paper liners.
In a large mixing bowl, whisk together the flour, cinnamon, baking soda, baking powder, and salt.
In another bowl, beat together the eggs, sugar, oil, and vanilla extract until well combined.
Stir in the shredded zucchini to the wet mixture.
Gradually fold the dry ingredients into the wet mixture until just combined.
Gently fold in the chocolate chips and walnuts, if using.
Scoop the batter into the prepared muffin tin, filling each cup about 2/3 full.
Bake for about 18-20 minutes, or until a toothpick inserted comes out clean.
Let the muffins cool in the tin for 5 minutes before transferring to a wire rack.
