Bring a large pot of salted water to a boil. Wash and dry produce.

Trim and quarter zucchini lengthwise; cut crosswise into ½-inch-thick pieces. Peel and mince garlic. Zest and quarter lemon.

Once water is boiling, add spaghetti to pot. Cook, stirring occasionally, until al dente, 9-11 minutes.

Reserve 1 cup pasta cooking water, then drain. (Keep empty pot handy for step 5.)

While pasta cooks, heat a drizzle of olive oil in a large, preferably nonstick, pan over medium-high heat. Add zucchini; cook, stirring occasionally, until browned and softened, 4-6 minutes. Season with salt and pepper.

Turn off heat; transfer to a plate. Wipe out pan.

Meanwhile, pat chicken* dry with paper towels and season all over with Italian Seasoning, salt, and pepper.

Once zucchini is done, heat a large drizzle of oil in same pan over medium-high heat. Add chicken and cook until browned and cooked through, 3-5 minutes per side.

Turn off heat; transfer to a cutting board to rest.

Heat a drizzle of olive oil in pot used for spaghetti over medium-high heat. Add garlic, half the lemon zest, and a pinch of chili flakes. Cook, stirring, until fragrant, 20-30 seconds.

Stir in ½ cup reserved pasta cooking water (¾ cup for 4 servings), stock concentrate, and juice from two lemon wedges (four wedges for 4). Simmer until thickened, 1-2 minutes. Turn off heat.

Add drained spaghetti, zucchini, sour cream, and 1 TBSP butter (2 TBSP for 4 servings) to pot with sauce; toss to coat.

Add half the Parmesan and season with salt and pepper. TIP: If needed, stir in more reserved pasta cooking water a splash at a time until spaghetti is coated in a creamy sauce.

Divide pasta between bowls. Top with chicken, remaining Parmesan, remaining lemon zest, and a pinch of chili flakes if desired. Serve with any remaining lemon wedges on the side.