In a skillet cook the bacon until crisp. Drain the bacon on paper towels and crumble it. Set aside. Remove the fat from the skillet, leaving a coating remaining. To this, add the chopped onion, and cook gently until transparent. Add the garlic and chopped greens, keeping the greens moving so as not to overcook. A tablespoon of water can be added to provide some steam for wilting. While greens are still in pan, drizzle with the balsamic vinegar and stir to coat. Add the chick peas, drained if from a can. Wilt the greens until they are just softened, but not to the point of being mush. Remove from pan and stir in crumbled bacon. Season to taste with salt and pepper. Sprinkle with lemon zest. Serve immediately.