Wash and dry all produce. Zest and halve lemon. Pat chicken dry with paper towels. Place in a large bowl or zip-close bag along with zest, juice from 1 lemon half, 11/2 tsp Italian Seasoning (we’ll use the rest later), and a large drizzle of olive oil. Season with salt and pepper. Toss to coat, then set aside.

Cut potatoes into 1/2-inch cubes. Place in a medium pot with enough salted water to cover by 2 inches. Bring to a boil and cook until tender, about 15 minutes. Meanwhile, trim and thinly slice scallions, separating whites from greens. Once potatoes are done, reserve 1/4 cup cooking water, then drain.

Return pot to low heat and add 1 TBSP butter and scallion whites. Cook, stirring, until softened, 1-2 minutes. Return potatoes to pot and mash until smooth, adding cooking water as needed to loosen. Stir in cheese, then season with plenty of salt and pepper. Keep over low heat until meal is ready.

While potatoes cook, halve tomatoes. Halve, peel, and thinly slice shallot. Halve zucchini lengthwise. Scoop out seeds with a spoon and discard, then slice crosswise into 1/2-inch-thick half-moons. Heat a large drizzle of olive oil in a large pan over medium-high heat. Add zucchini; season with salt and pepper. Cook, stirring, until just softened, 3-5 minutes. Add tomatoes, shallot, and 1 TBSP butter. Cook until softened, 2-3 minutes. Transfer veggies to a second large bowl, then wipe out pan.

Heat a drizzle of olive oil in same pan over medium-high heat. Remove chicken from marinade, shaking off excess moisture. Season all over with salt, pepper, and remaining Italian Seasoning. Add to pan and cook until browned and cooked through, 3-6 minutes per side. Remove from pan and let rest on a plate for about 3 minutes. Wipe out pan, return to medium-high heat, and stir in 1/4 cup water and stock concentrate.

Stir 1 TBSP butter and a squeeze or two of lemon into pan. Simmer until reduced, 2-4 minutes. Season with salt and pepper. Stir in any juices released by chicken. Stir half the scallion greens into potatoes in pot, then divide between plates along with veggies and chicken. Spoon pan sauce over everything. Garnish with remaining scallion greens.