Begin by gathering all the necessary ingredients. Preheat your oven to 400 degrees Fahrenheit (200 degrees Celsius). Prepare a 9x5-inch loaf pan by applying cooking spray to its interior.

In a large skillet, heat the olive oil over medium heat. Sauté the diced bell pepper and onion until the onion turns translucent and the bell pepper softens, which should take about 5 to 10 minutes. Add the minced garlic and cook until fragrant, approximately 1 to 2 minutes, before removing the skillet from the heat.

In a spacious bowl, combine the ground beef, whole wheat bread crumbs, shredded carrot, shredded zucchini, eggs, salt, pepper, and the cooked bell pepper mixture. Mix thoroughly using your hands, ensuring all ingredients are well incorporated. Transfer the mixture into the prepared loaf pan, pressing it down firmly.

Bake the meatloaf in the preheated oven until the center is no longer pink, which will take around 35 to 40 minutes. To verify doneness, use an instant-read thermometer; it should register at least 160 degrees Fahrenheit (70 degrees Celsius).

Once cooked, spread ketchup over the top of the meatloaf and return it to the oven for an additional 5 minutes, or until the ketchup is bubbling.