Pour 1 teaspoon of lemon juice over the grated zucchini.
Add in all the ingredients into a mixing bowl and mix the ingredients either using hands or an electric mixer (mix at the lowest level) until a sticky dough is form.
Cut out a small piece of a parchment paper. Place it into the baking dish or the loaf tin.
Transfer the whole grain rye chocolate zucchini bread dough evenly into the dish or loaf tin. Smooth out the surface of the sourdough with a moist spoon/ knife.
Cover the baking dish or tin with a small plastic bag to prevent the bread dough from drying out. The bag should be higher than the dish/tin. This would prevent the dough from sticking to the plastic bag. After which, keep the bowl in a warm place (about 21 °C - 23 °C) for 23 to 24 hours.
The chocolate zucchini bread dough should double in size. The sourdough should fill the baking dish/ loaf tin. Bake the dough, when it reaches the maximum height.
Preheat baking oven to 250 °C.
Reduce the heat to 200 °C. Place an extra baking tray upside down into the highest level of the baking tray and bake the baby chocolate zucchini for 17 minutes. It depends on your baking oven, you might need to adjust the baking time accordingly. Just have fun and try it out.
Remove the top baking tray (be careful, it is very hot!) and continue to bake the bread for another 8 minutes.
After baking, place the chocolate zucchini bread on a cooling tray and allow it to cool down completely. Thereafter, remove the parchment paper gently and store it in a cloth bag. Serve this sourdough plain or with some homemade baby fruit jam for breakfast. Finish it within 3-4 days.