In a large skillet, heat olive oil over medium heat. Add the diced red onion and minced garlic, cooking until the onion is translucent, about 3-4 minutes.
Add the sliced zucchinis to the skillet. Sauté for another 5 minutes until they begin to soften.
Stir in the shredded chicken and halved cherry tomatoes, mixing well to combine. Season with Italian seasoning, salt, and pepper. Remove from heat.
In a greased baking dish, layer the chicken and zucchini mixture evenly across the bottom.
Sprinkle mozzarella cheese generously over the top, followed by the grated Parmesan cheese.
Cover the baking dish with aluminum foil and bake in the preheated oven for 20 minutes.
Remove the foil and bake uncovered for an additional 10-15 minutes or until the cheese is bubbly and golden brown.
Once done, remove from the oven and let it rest for 5 minutes before serving.
Garnish with fresh basil leaves before serving for a pop of color and flavor.