In a large bowl, cream the butter, oil and sugar until light and fluffy. Beat in the eggs, milk and vanilla. Combine the flour, cocoa, baking soda, salt and cinnamon; gradually add to creamed mixture. Fold in zucchini and chocolate chips.
Fill greased or paper-lined muffin cups two-thirds full. Top with pecans. Bake at 375° for 20-25 minutes or until a toothpick comes out clean. Cool for 10 minutes before removing from pans to wire racks to cool completely.