Preheat oven to 350F/180C and line your muffin tin with paper liners.
In a medium bowl combine sifted flour, oats, cocoa, baking powder, baking soda, salt, sugar.
In a large bowl beat eggs, oil, yogurt, chocolate essence and vanilla.
Stir in grated zucchini and then add dry ingredients to the bowl.
Divide muffin batter evenly among 18 small or 12 large muffins cups.
Bake in the oven for 20-25 minutes.