Preheat the oven to 375°F (190°C).
Cut each zucchini in half lengthwise. Use a spoon to scoop out the flesh, leaving a 1/4-inch thick shell. Reserve the flesh.
In a large bowl, combine the cooked quinoa, black beans, corn, red bell pepper, onion, garlic, cumin, chili powder, paprika, salt, and pepper. Mix well.
Add the reserved zucchini flesh to the bowl and mix until combined.
Place the zucchini shells on a baking sheet. Fill each shell with the quinoa and black bean mixture.
Sprinkle the shredded cheddar cheese on top of each stuffed zucchini.
Bake in the preheated oven for 20-25 minutes, or until the zucchini is tender.
Garnish with fresh cilantro before serving.