Preheat the oven to 325 degrees F (165 degrees C).
Mix flours, sugars, baking soda, nutmeg, cinnamon, and salt together in a large bowl. Fold in the following ingredients, one at a time and with a rubber spatula, in the order listed: vanilla, eggs, vegetable oil, lemon juice, and zucchini. Divide the mixture between two loaf pans.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, 65 to 75 minutes. Cool in the pans for 10 minutes before removing to cool completely on a wire rack.