Step 1

Preheat the oven to 360 F. Lightly coat (2 or 7 x 3 x 2 mini loaf pans or (9 x 5-inch loaf pan with butter. Note: Using 2 mini loaf pans instead of 3 will you get you slightly taller loaves.

Step 2

Using a box grater, grate the zucchini on an angle on the side with largest holes. No need to drain out the excess water. Set aside.

Step 3

Add the banana, sugar, and vanilla to a large mixing bowl. Cream with a hand held mixer or stand mixer fitted with the paddle attachment, about 30 seconds to 1 minute (some small lumps of banana are okay).

Step 4

Add the eggs, one at a time until fully incorporated. Add the sourdough starter.

Step 5

Sift the flour, cinnamon, nutmeg, baking soda, and salt together in a separate bowl. Working in batches, add this to the banana mixture.

Step 6

Add the oil and milk and mix until just combined. Do not over do it; the banana bread will be tough. The texture should be thick and pourable, but not runny. Add more flour if needed. Fold in the grated zucchini.

Step 7

Pour the batter into the prepared pan(s). For 2 mini loaf pans, fill about 3/4’s full. For 3 mini loaf pans, fill about 2/3’s full (these loaves will not be as high). Place onto a baking sheet and transfer to the oven.

Step 8

Bake for 40-45 minutes for the 2 mini loaf pans (about 30-35 minutes if using 3 mini pans) or 60-65 minutes or more for the standard 9 x 5-inch pan. Cover with foil if the loaf browns too quickly.

Step 9

Cool in the pan for 20 minutes, and then transfer to a wire rack to cool completely.