Preheat oven to 350℉ convection if available. Grease 12 muffin cups, line with paper muffin liners, or set up silicon cups on a sheet pan.
Combine flour, baking soda, cinnamon, and salt in a medium bowl. In a large bowl, beat the egg then add sugar, oil, milk, lemon zest, and vanilla extract. Add the dry ingredients and stir until just moistened. Fold in zucchini, chocolate chips, and nuts. Fill prepared muffin cups nearly full.
Bake for about 25 minutes until a toothpick inserted into the center of a muffin comes out clean and the muffin springs back when lightly touched.