Gather all ingredients.

Preheat the oven to 350 degrees F (175 degrees C). Grease a 12-cup muffin tin or line cups with paper liners.

Combine flour, sugar, baking soda, cinnamon, and salt in a large bowl.

Whisk oil, milk, egg, lemon juice, and vanilla extract in a separate bowl.

Stir oil mixture into flour mixture until just moistened; fold in zucchini, chocolate chips, and walnuts.

Spoon batter into the prepared muffin cups, filling each 2/3 full.

Bake in the preheated oven until tops spring back when lightly pressed, about 20 to 25 minutes. Let muffins cool in the tin briefly before transferring to a wire rack to cool completely

Enjoy!