Bring a large pot of salted water to a boil over high heat: add sugar, and beans. Cook until beans are bright green and tender, 3 to 5 minutes. Drain, and place in a large bowl of ice water to stop cooking.
Combine the butter and olive oil in a large skillet over medium-high heat; cook until butter melts. Stir in the garlic; cook until pale beige and fragrant. Stir in the beans; cook until wilted, and garlic is dark brown, about 4 minutes. Toss beans with parsley and lemon zest, and cook 1 to 2 minutes more. Season to taste with salt and pepper. Transfer beans to a serving dish, and garnish with lemon wedges.