This comes from a cookbook called Okanagan Harvest. I tried it and it's delicious!
Chocolate Zucchini Cake

1/2 c. margarine
1/2 c. oil
1 3/4 c. sugar
2 eggs
1 tsp. vanilla
1/2 c. sour milk
4 tbsp. cocoa
2 1/2 c. flour
1 tsp. baking soda
2 c. unpeeled zucchini, shredded
1/4 c. chocolate chips
1/2 tsp. cinnamon
1/2 tsp. cloves
1/2 tsp. salt

Cream together the margarine, oil, and sugar. Add the eggs, vanilla and milk and beat well. Sift together the flour, cocoa, soda, cinnamon, cloves and salt. Gradually add to the creamed mixture. Stir in the zucchini and mix well. Pour into a greased and floured 9x13" pan. sprinkle with chocolate chips. Bake for 40 to 45 minutes at 325 degrees F. for a glass pan, 350 degrees F. for metal.