For the sourdough bread with zucchini, prepare the pre-dough in the evening: To do this, mix lukewarm water with the basic mixture and the baking ferment. Add the rye flour and mix well. Cover with a dish and let stand overnight in a warm place (approx. 30 °C, possibly place the bowl next to or under a lamp).
The next day, stir salt into the lukewarm water and add to the pre-dough with rye and wheat flour and the whole spices. Knead well.
Wash, dry and coarsely grate the zucchini. Mix with the dough. Pour the dough into about 3 loaf pans – the pans should only be filled about halfway, as the dough should still rise. Cover the loaf pans and let the dough rise in a warm place (about 30 °C).
Cover the loaf pans with aluminum foil and bake the bread in a preheated oven at 210 °C top and bottom heat for 1 hour. Remove the foil and bake the bread for another 30 minutes. Then let the bread rest in the turned-off oven for another 15 minutes.
Turn out the sourdough bread with zucchini from the molds and enjoy.