Preheat oven to 400°F (200°C) and grease a 9x13 inch baking dish.
Using a spoon, scoop out the flesh of the halved zucchini to create a boat shape with 1/4-inch thick walls. Roughly chopped the removed flesh and set aside.
In a large skillet over medium-high heat, brown the ground beef and onion until the meat is no longer pink. Drain any excess grease.
Add the minced garlic, chopped zucchini flesh, chili powder, cumin, and paprika to the skillet. Sauté for 3 to 4 minutes until the zucchini flesh softens.
Stir in the black beans, corn, and tomato sauce. Reduce heat and simmer for 5 minutes. Season with salt and pepper.
Arrange the zucchini boats in the prepared baking dish. Divide the beef mixture evenly among the shells, pressing down slightly.
Cover the baking dish with aluminum foil and bake for 20 minutes.
Remove the foil, sprinkle the shredded cheese over the boats, and bake for an additional 5 minutes until the cheese is melted and bubbly.
Garnish with fresh cilantro and serve immediately.