Grease bottoms only of 2 9x5x3-inch loaf pans with non-stick cooking spray.
Cut off the stem end of each of the 3 zucchini and shred the zucchini.
Crack 4 eggs, add to a large bowl, and beat until just mixed.
Add zucchini, 1 ⅔ cups sugar, ⅔ cup vegetable oil, and 2 teaspoons vanilla extract to eggs and mix.
In a separate bowl, mix 3 cups all-purpose flour, 2 teaspoons baking soda, 1 teaspoon ground cinnamon, and ½ teaspoon baking powder.
Add dry ingredients to zucchini mixture and stir gently until well mixed.
Pour into prepared loaf pans.
Bake 50 to 60 minutes (until knife inserted in center comes out clean).
Cool in pan for 10 minutes.
Loosen sides of loaves and remove from pans.
Notes
Zucchini bread will last up to a year in the freezer if wrapped tightly to prevent air from being locked in the wrap. I suggest cooling completely, then securing tightly with plastic wrap and then wrapping in foil. Label with the name and date.