Chop the chocolate, coarsely grate the zucchini and puree the bananas with a hand blender. Mix the oil, sugar, vanilla flavor and mashed bananas together well. Stir in the grated zucchini.
Mix the flour, cocoa, baking powder, cinnamon and salt in a separate key. Fold the dry ingredients and then the chopped chocolate into the liquid ingredients.
Put the dough in an oiled and floured 2 liter loaf pan and bake on the middle rack for 60 minutes. After baking, let the cake cool in the tin for 30 minutes before turning it out.
The cake tastes best after being wrapped in cling film in the refrigerator overnight. If you keep it in this form, it will still be juicy even after more than a week.
For a vegan cake you should make sure that the chocolate used does not contain any milk components. If the cake doesn`t have to be vegan, the bananas can be replaced with three eggs.