Preheat your oven to 350°F and generously grease four mini loaf pans with oil or butter, making sure to coat the bottom and all sides to prevent sticking. This gives you time to prep ingredients while the oven reaches temperature.
In a medium bowl, whisk together the flour, baking soda, baking powder, salt, apple pie spice, cinnamon, and allspice. Mixing these dry ingredients thoroughly ensures the leavening agents and spices are evenly distributed throughout the batter, which prevents streaky flavors and uneven rise. I like to sift these together if you have a sifter—it really helps break up any lumps in the cinnamon and allspice.
While the oven heats, shred the zucchini finely using a box grater or food processor. Place the shredded zucchini in a clean kitchen towel and squeeze firmly to remove as much excess moisture as possible—this is crucial because zucchini releases a lot of water as it cooks, and removing it prevents the bread from becoming soggy or dense.
In a large bowl, whisk together the sugar, room temperature eggs, oil, applesauce, vanilla extract, and lemon zest until well combined and slightly emulsified. The room temperature eggs are important here because they blend more smoothly with the other ingredients, creating a more cohesive batter. This mixture will be the foundation that carries all your flavors.
Pour the dry ingredient mixture from Step 2 into the wet ingredient base from Step 4, stirring gently until just combined—don't overmix, as this can develop gluten and make the bread tough. Fold in the squeezed zucchini from Step 3 and the chopped walnuts until evenly distributed throughout the batter. I like to use a rubber spatula and fold with a gentle hand—mixing just until you don't see dry flour streaks anymore.
Divide the batter evenly among the four prepared pans from Step 1, filling each about three-quarters full. Place pans on the middle rack of your preheated 350°F oven and bake for 35-40 minutes, until a toothpick inserted into the center comes out clean or with just a few moist crumbs (not wet batter). The bread is done when the tops are golden brown and spring back slightly when gently touched.
Remove the pans from the oven and let them cool in the pans for about 5 minutes—this allows the bread to set slightly and firm up enough to handle without falling apart. Turn each mini loaf out onto a wire cooling rack and let cool completely before slicing or storing.