Preheat oven to 175 degrees celcius
Line a 12 hole muffin tin with paper cases
In a large bowl cream the butter and sugar until light and creamy
Add eggs one at a time, beating well after each addition
Stir in the yoghurt and milk if using
In a separate bowl combine the flour, cacao, baking powder, bicarb of soda and salt
Pour into the creamed mixture and fold ingredients together until just combined
Fold in zucchinis and carrots
Fill the paper case until 2/3 full
Bake for approximately 2o – 25 minutes or when toothpick comes out clean
Cool in the tray for 10 minutes then turn out onto wire rack.