Preheat the oven to 350°F.
Grease or line a 9x5-inch loaf pan with parchment paper.
In a large bowl, whisk the oil and eggs. I make this bread by hand, but you can use a mixer if you want.
Add the zucchini, carrots, and apples. Use a large spoon to mix it well.
Mix in all the dry ingredients except the walnuts. Take your time to be sure to mix in all the flour to get a wet batter.
Stir in the walnuts.
Spread the batter evenly into the prepared pan. To prevent a dome top, make about a 3-inch-long little indent across the batter with a spoon. This prevents the top from being too high.
Bake at 350°F. for 55-65 minutes or until a cake tester inserted in the middle comes out clean. If it is browning too fast around the edges, cover it with a tent of aluminum foil. I cut out a small square in the middle of the tent. See the picture in the slideshow.
Cool the loaf bread in the pan on a wire rack for 10 minutes. Remove it from the pan and transfer the loaf bread to the wire rack to finish cooling.
Store the loaf bread covered at room temperature.