Adjust rack to top position and preheat oven to 425 degrees. Bring a medium pot of salted water to a boil. Wash and dry all produce. Trim and halve zucchini lengthwise; thinly slice into half-moons. Pat chicken dry with paper towels and season all over with salt, pepper, and half the Italian Seasoning (you’ll use the rest later).

Heat a drizzle of olive oil in a large, preferably ovenproof, pan over mediumhigh heat. Add chicken and cook until golden brown but yet not cooked through, 1-2 minutes per side. Transfer to a baking sheet and roast on top rack until cooked through, 12-15 minutes. Set chicken aside and heat broiler to high or oven to 500 degrees.

While chicken cooks, heat a drizzle of olive oil in pan used for chicken over medium-high heat. Add zucchini and cook until browned and tender, 5-7 minutes. Remove from pan and set aside. Meanwhile, add penne to pot of boiling water. Cook until al dente, 9-11 minutes. Reserve 1/2 cup pasta cooking water, then drain.

Heat a drizzle of olive oil in pan used for zucchini over medium heat. Add remaining Italian seasoning and a small pinch of chili flakes if desired; cook until fragrant, 30 seconds. Stir in marinara and a big pinch of salt. Bring to a simmer.

Add penne, zucchini, and 2 TBSP butter (3 TBSP for 4) to pan with simmering sauce; season with salt and pepper. Toss to combine. If needed, stir in reserved pasta cooking water a splash at a time until everything is thoroughly coated in sauce. TIP: If your pan isn’t ovenproof, transfer pasta now to a baking dish.

Top pasta with chicken, then sprinkle with mozzarella and Parmesan. (TIP: If you like, slice chicken and toss with pasta before topping with cheese.) Broil or bake on top rack until cheese is melted and lightly browned, 2-3 minutes. Sprinkle with chili flakes if desired. Divide between plates and serve.