1. Preheat oven to 350 degrees F (175 degrees C), grease and flour a 9x13 inch pan.
2. Cream butter, oil and sugar until light and fluffy.
3. Add eggs, vanilla and sour milk. Beat until smooth.
4. Mix flour, cocoa, baking soda and cinnamon together and add to creamed mixture. Beat well. Stir in diced zucchini.
5. Pour into a 9x13 inch pan and sprinkle top with chocolate chips.
6. Bake at 350 degrees F (175 degrees C) for 40 to 45 minutes, or until a toothpick inserted into the center comes out clean.
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