Preheat oven to 350°F. Spray a 9×5-loaf pan with nonstick cooking spray, flour sides.
Squeeze zucchini until dry in a kitchen towel.
In a large bowl, whisk the flour, sugar, flaxseed, baking powder, cardamom, salt, and baking soda.
In a medium bowl whisk the yogurt, eggs, oil, and lemon zest; stir in zucchini.
Add zucchini mixture and walnuts to flour mixture, stirring until well combined. Pour batter into prepared pan. Bake 55-60 minutes or until a wooden pick inserted in center comes out clean.
Cool in pan 10 minutes on a wire rack. Remove bread from pan; place on wire rack. Makes 1 loaf, 16 servings.
