Prep your pan and oven: Heat the oven to 350°F (175°C). Line a 9x5-inch loaf pan with parchment, leaving a little overhang for easy lifting.
Lightly grease the sides.
Grate the zucchini: Use the small holes of a box grater. Place the grated zucchini in a clean kitchen towel and gently squeeze out excess moisture. Don’t wring it dry—just remove the drips.
Mix dry ingredients: In a large bowl, whisk flour, sugar, baking powder, baking soda, and salt until evenly combined.
Stir in the lemon zest.
Mix wet ingredients: In a separate bowl or large measuring cup, whisk lemon juice, non-dairy milk, oil, and vanilla until smooth.
Combine: Pour the wet mixture into the dry ingredients. Stir gently with a spatula until almost combined—some small streaks of flour are okay.
Fold in zucchini: Add the grated zucchini (and any optional add-ins). Fold just until incorporated.
The batter should be thick but scoopable.
Bake: Transfer the batter to the loaf pan and smooth the top. Bake for 45–55 minutes, or until a toothpick inserted in the center comes out clean or with a few moist crumbs.
Cool: Let the loaf cool in the pan for 10–15 minutes, then lift it out and cool completely on a rack. Don’t glaze while hot or it will melt away.
Glaze (optional but lovely): Whisk powdered sugar with lemon juice until smooth and pourable.
Drizzle over the cooled loaf. Let set for 15 minutes before slicing.