Heat olive oil in a large, oven-safe skillet over medium heat. Season chicken tenderloins with chili powder, cumin, salt, and pepper. Cook for 2-3 minutes per side, until lightly browned. Remove chicken from the skillet and set aside.
In the same skillet, add the quinoa and water or broth. Stir to combine and turn heat on high. Stir frequently until water is absorbed and quinoa is cooked (about 5 minutes)
Turn heat to medium and add bell pepper, zucchini and enchilada sauce and stir for 4-5 minutes to cook vegetables.
Cut cooked chicken into 1 inch pieces and nestle into the quinoa. Stir in drained black beans.
Sprinkle the shredded Mexican cheese evenly over the top and broil in the oven for 3-5 minutes or until cheese is melted.
Garnish with optional toppings like cilantro, jalapeños, sour cream, or diced avocado.