Preheat your oven to 375°F (190°C).
Cut the zucchinis in half lengthwise and scoop out the seeds to create boats. Place them cut-side up in a baking dish.
In a large bowl, combine the cooked quinoa, diced tomatoes, black beans, chili powder, cumin, garlic powder, onion powder, salt, and pepper. Mix well.
Spoon the quinoa mixture evenly into each zucchini half, pressing down gently to pack it in.
Top each stuffed zucchini with shredded cheese.
Cover the baking dish with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes, or until the zucchinis are tender and the cheese is bubbly and golden.
Remove from the oven and let cool for a few minutes. Garnish with fresh cilantro if desired before serving.