Place the flour, starter, sugar, banana, butter and milk in a big mixing bowl and stir till mixed. Cowl tightly and place within the fridge for twenty-four hours.
The next day, take away the dough combination and let sit out on the counter for about 4 hours so it reaches room temperature.
Preheat the oven to 350ºF and modify the rack to the center place. Line a muffin tin with unbleached parchment liners.
Switch the flour combination to the bowl of a standing mixer. It’s also possible to use hand-held beaters.
In a medium-size bowl, mix the zucchini, vanilla, eggs and yogurt. Whisk to mix. Stir within the cinnamon, nutmeg, baking soda and salt after which instantly, add the zucchini combination into the flour combination and blend on low utilizing the beater. Combine till simply mixed and don’t over combine (it will make the dough robust).
Spoon equal parts of dough into every muffin cup, filling the cups about 3/4 full. Bake for 25-28 minutes, till simply turning golden brown. Take away from oven and funky. Repeat with remaining batter.
Leftovers may be frozen after which reheated within the oven, or retailer within the fridge for 3-4 days and reheat within the oven earlier than serving.