In a large mixing bowl, beat the butter, oil, and sugar. Add the eggs, milk, and vanilla; mix well. Combine the flour, cocoa, baking soda, salt, and cinnamon; add to the creamed mixture. Fold in zucchini and chocolate chips.
Fill greased or paper-lined muffin cups two-thirds full. Top with pecans. Bake at 375°F for 20 to 25 minutes or until top springs back when lightly touched. Cool for 10 minutes before removing from pans to wire racks to cool completely.