Bring a large pot of salted water to boil. Wash and dry all produce. Trim and quarter zucchini lengthwise; cut crosswise into 1/2-inch-thick pieces. Trim and thinly slice mushrooms. Halve tomatoes. Mince chives. Quarter lemon.

Heat a drizzle of olive oil in a large pan over medium-high heat. Add zucchini and season with salt and pepper. Cook, stirring occasionally, until golden brown and softened, 4-6 minutes. Transfer to a medium bowl.

Heat a large drizzle of olive oil in pan used for zucchini over medium-high heat. Add mushrooms and cook, stirring occasionally, until golden brown and slightly crispy, 5-7 minutes. Turn off heat; season with salt and pepper, then transfer to bowl with zucchini. Wash out pan.

Once water is boiling, add penne to pot. Cook until al dente, 9-11 minutes. Reserve 1 cup pasta cooking water, then drain well.

Meanwhile, heat 1 TBSP butter (2 TBSP for 4 servings) and a drizzle of olive oil in pan used for mushrooms over medium-high heat. Add tomatoes and season with salt, pepper, and Italian Seasoning. Cook, stirring, until tomatoes are softened, 2-4 minutes. Stir in half the chives and juice from half the lemon. Reduce heat to low, then stir in stock concentrate and 1/4 cup reserved pasta cooking water (1/3 cup for 4). Whisk in crème fraîche; season with salt and pepper.

Add zucchini, mushrooms, and drained penne to pan with sauce; stir to combine. Stir in 1 TBSP butter (2 TBSP for 4 servings) until melted. (TIP: If necessary, add more reserved pasta cooking water a splash at a time until penne is coated in a creamy sauce.) Divide pasta between plates. Sprinkle with Parmesan and remaining chives. Serve with remaining lemon wedges on the side.