Adjust racks to top and middle positions and preheat oven to 425 degrees. Wash and dry all produce. Cut sweet potatoes into ½-inch cubes. Toss on a baking sheet with a drizzle of olive oil, salt, and pepper. Roast on top rack until browned and tender, about 20 minutes.

While sweet potatoes roast, trim and halve zucchini lengthwise. Cut crosswise into ½-inch-thick half moons. Toss on a second baking sheet with a large drizzle of olive oil, salt, and pepper. Roast on middle rack, flipping halfway through, until browned and tender, about 15 minutes.

While zucchini roasts, halve, peel, and mince shallot. Strip rosemary leaves from stems; finely chop leaves until you have 1 tsp (2 tsp for 4 servings).

Pat chicken dry with paper towels; season all over with salt and pepper. Heat a drizzle of oil in a large pan over medium-high heat. Add chicken and cook until browned and cooked through, 5-7 minutes per side. Turn off heat; transfer to a cutting board and set aside to rest.

Heat a drizzle of olive oil in same pan over medium heat. Add shallot and chopped rosemary. Cook, stirring, until softened, 2-3 minutes. Stir in vinegar and jam. Simmer until syrupy, about 1 minute. Stir in stock concentrate and ¼ cup water (⅓ cup for 4 servings). Let reduce until saucy, about 3 minutes. Turn off heat. Stir in 1 TBSP butter (2 TBSP for 4 servings) until melted. Season with salt and pepper.

Thinly slice chicken crosswise. Divide chicken, sweet potatoes, and zucchini between plates. Drizzle chicken with sauce.