Line 12 muffin cups with paper liners, or spray with nonstick spray.
In a medium sized bowl, mix flours, sugar, baking soda, cinnamon and salt. Set aside.
In a small bowl, whisk together egg, oil, milk, lemon juice and vanilla. Stir wet ingredients into dry ingredients just until moistened. Stir in zucchini, chocolate chips and walnuts just until combined.
Fill prepared muffin cups 2/3 full.
Bake for 20-25 minutes or until toothpick inserted into center comes out clean.
Cool for five minutes in pan and then remove muffins to a wire rack to cool completely.