Fill a large skillet one-quarter full with water, add 1 tablespoon salt and bring to a boil. Add the green beans, cover and simmer until bright green but still slightly hard, 3 to 5 minutes. Drain and set aside.
Heat the olive oil in the same skillet over medium-high heat. Add the garlic and saute until fragrant, 30 seconds. Add the green beans; saute for 2 minutes. Add the balsamic reduction and 1/4 teaspoon salt and pepper. Toss the beans to coat, then cook for 1 minute more. Transfer to a platter and sprinkle with the lemon zest.