Melt the chocolate in a bain-marie. In a bowl, mix the dried ingredients (sugar, flour and baking powder) and then add the oil, the zucchini/courgettes (previously minced in a food processor) and the melted chocolate. Line a 24-cm/9-inch baking pan with parchment paper and bake in a not-preheated oven for 50 minutes at 180° C or 350° F.