Preheat oven to 400°F (200°C).
In a large mixing bowl, toss the chicken cubes and zucchini slices with olive oil, garlic powder, oregano, salt, and pepper until evenly coated.
Spread the mixture in a single layer into a 9x13 inch baking dish.
Pour the marinara sauce evenly over the chicken and zucchini mixture.
Bake for 20 minutes or until the chicken reaches an internal temperature of 165°F (74°C).
Remove from oven and sprinkle the mozzarella and Parmesan cheeses over the top.
Return to the oven and bake for an additional 10 minutes until the cheese is melted and slightly browned.
Let rest for 5 minutes before serving.