This recipe comes from the Penzeys Spices catalog. Great for school-day breakfasts or lunches. I substitute 1/2 cup of the flour for whole wheat pastry flour for an extra health kick. It doesn't change the flavor at all.
Preheat oven to 325. Line 2 standard muffin pans with muffin papers.
Mix together the milk and vinegar and set aside.
In a large bowl, beat together the butter, oil and sugar until creamy. Add eggs, vanilla extract and milk/vinegar mix. Blend well.
In a separate bowl, mix together flour, cocoa powder, baking soda, cinnamon and salt. Add to the butter mixture and stir by hand to combine.
Add grated zucchini and half the chocolate chips and stir well.
Spoon the batter evenly into the pans, filling each cup 2/3 full. Sprinkle the other half of the chocolate chips and nuts (if using) on top and bake for about 20 minutes until a toothpick inserted in the center comes out clean or the muffins spring back when lightly touched.