Preheat oven to 350F or 325F (convection).
Wash eggplant and zucchini, then cut the ends off of each. Grate in a food processor using the fine blade. Measure out grated amounts, then transfer to a colander and press gently to squeeze out excess moisture. Place on a clean towel and press again to dry further.
In a separate bowl, whisk together dry ingredients then set aside.
In a large mixing bowl, beat oil and sugar until lighter, approximately 3-4 minutes. Add extract and eggs or aquafaba, mixing well. Slowly stir in the dry ingredients until incorporated, then fold in grated eggplant and zucchini. Add nuts, if using.
Spoon thick batter into loaf pans lined with parchment or oiled well. Batter is sufficient for two 9x4 or 9x5 loaf pans or 6 mini loaf pans.
Bake small pans for 20-25 minutes, larger pans for 40-45 minutes, testing with a toothpick before removing from the oven. A toothpick inserted into the center of each loaf should come out with dry crumbs or clean, but not wet.
Remove to cool on wire racks. Store in sealed containers at room temperature when fully cooled.