Adjust an oven rack to middle position and preheat the oven to 375 degrees. Generously coat a 9-inch by 5-inch loaf pan with cooking spray. Chop the ends off the zucchini (just 1/4-inch off each end) and finely shred the zucchini, peel and all. Place the shredded zucchini in a clean kitchen towel, wrap the towel, and wring the ends to squeeze out all the excess water. You should have about 1 to 1 1/2 cups of dry zucchini. Set the zucchini aside.

In a large bowl, whisk together the flour, baking soda, baking powder, cinnamon, allspice, and salt. In a smaller bowl, whisk the sugar, yogurt, eggs, lemon juice or sour cream, and butter until combined. Gently fold the yogurt mixture and zucchini into the flour mixture, using a rubber spatula to fold the ingredients together until just combined. Transfer the batter to the prepared pan.

Bake until golden brown and a think knife or skewer inserted in the center comes out with a few crumbs attached, 45-55 minutes. Cool for 10 minutes then turn out into wire rack to cool for at least 1 hour. Store well-covered for up to three days.