Heat the oven to 375 degrees. In a large bowl, combine the ground beef, grated carrots, chopped spinach, diced onion, breadcrumbs, egg, salt, and black pepper. Mix until evenly blended.
Shape the mixture into a loaf and place it on a baking sheet lined with parchment paper. Bake for 45 minutes until the internal temperature reaches 160 degrees.
While the meatloaf bakes, use a spiralizer or vegetable peeler to turn the zucchini into noodles. Set them aside.
In a skillet over medium heat, warm the olive oil and add the minced garlic. Cook for one minute, then stir in the tomato sauce and Italian herbs. Simmer gently for 10 minutes.
In the last five minutes of the meatloaf cooking time, add the zucchini noodles to the sauce and toss to coat. Cook just until the noodles soften slightly.
Remove the meatloaf from the oven and let it rest for five minutes before slicing. Serve slices over the zucchini noodles and sauce.