Whisk together the flour, cinnamon, baking powder, baking soda, and salt in a medium bowl.
Add the eggs to a large bowl and whisk lightly to break them up. Then add in the oil, granulated sugar, and vanilla extract and whisk until combined.
Use a spatula or wooden spoon to stir the dry ingredients into the wet. Batter will be very, very thick and almost unstir-able.
Stir the grated, drained zucchini into the batter until all ingredients are completely combined and the batter is smooth and pourable.
Pour zucchini bread batter into the prepared loaf pans and bake at 325F for 40-60 minutes, or until a toothpick inserted into the center of each loaf comes out clean.
Cool zucchini bread in pan for 15-20 minutes, then run a butter knife around the inside edges of the pans. Tip the loaves onto a wire rack to finish cooling completely. Serve at room temperature (or toasted with butter!)