In a large bowl, combine the cooked shredded chicken, sliced zucchinis, cherry tomatoes, ranch dressing, garlic powder, Italian seasoning, salt, and pepper. Mix until well coated.
In a 9x13 inch baking dish, drizzle olive oil to coat the bottom.
Spread the chicken and zucchini mixture evenly into the dish.
Sprinkle the shredded mozzarella and grated Parmesan cheese evenly over the top.
Cover the dish with aluminum foil and bake in the preheated oven for 25 minutes.
Remove the foil and bake for an additional 15 minutes until the cheese is bubbly and golden brown.
Remove from the oven and let it sit for a few minutes before garnishing with fresh basil leaves if desired.
Scoop onto plates and enjoy your cheesy, comforting dish!