Preheat Oven: Preheat your oven to 375°F (190°C).

Sauté the Chicken: In a large skillet, heat olive oil and butter over medium-high heat. Add the bite-sized chicken pieces and season with salt and pepper. Cook until the chicken is golden and cooked through, about 5-6 minutes.

Add Vegetables: In the same skillet, add the diced zucchini, red bell pepper, and minced garlic. Sauté for 3-4 minutes until the vegetables are slightly tender. Add the corn kernels and cook for an additional 1-2 minutes.

Create a Roux: In the same skillet, sprinkle the flour over the remaining oil and butter. Continue stirring for 1-2 minutes to cook the flour, forming a smooth roux.

Add Liquids and Cheese: Gradually whisk in the chicken broth and half-and-half, cooking until the mixture thickens, about 3-4 minutes. Add the cubed cream cheese, stirring until it melts and the sauce becomes smooth.

Add Mozzarella: Stir in 1 cup of the shredded mozzarella cheese, allowing it to melt into the sauce.

Assemble the Casserole: In a large mixing bowl, combine the cooked chicken, sautéed vegetables, and creamy sauce. Stir thoroughly to coat all ingredients evenly, then transfer the mixture into a 9x13-inch baking dish. Top with the remaining ¼ cup of shredded mozzarella.

Bake the Casserole: Place the baking dish in the preheated oven and bake for 20-25 minutes, or until the casserole is bubbly and the cheese on top is melted and golden.

Garnish and Serve: Remove the casserole from the oven and let it cool for a few minutes.