Preheat the oven to 325 degrees Fahrenheit and grease and flour a 9-inch loaf pan.
Grate the zucchini using a box grater or food processor. Leave the peel on unless the zucchini is unusually tough or damaged. Do not squeeze out the moisture unless the zucchini seems extremely wet.
1 Cup Zucchini
In a medium mixing bowl, combine the flour, cinnamon, salt, baking soda, and baking powder.
1½ Cups All-purpose Flour, ½ Tsp Cinnamon, ½ Tsp Salt, ½ Tsp Baking Soda, ⅛ Tsp Baking Powder
Stir the egg whites and whole egg into the dry ingredients.
1½ 'Egg' Pasteurized Egg Whites, 1 Lrg Egg
Add the grated zucchini and sour cream, then stir until mixed.
1 Cup Zucchini, ¼ Cup Sour Cream
Stir in the oil, sugar, and vanilla extract until fully combined.
½ Cup White Sugar, ½ Cup Neutral Oil, ½ Tsp Vanilla Extract
Add the milk and stir until fully combined. The batter should soften noticeably and spread more easily, but should not become thin or pour like cake batter.
¼ Cup Milk
Bake about 1 hour and 20 minutes, or until the center tests clean and the top is golden brown.
A butter knife inserted at a slight angle toward the center should come out mostly clean. A few soft crumbs are fine, but wet batter means the loaf needs more baking time.
Let the zucchini bread cool briefly in the loaf pan before transferring to a wire rack to cool completely.