Warm olive oil in a large, nonstick skillet over medium-high heat. Add the sliced squash, toss in the olive oil, and cook for 1 minute. Carefully add 1 tablespoon water, cover, and cook until the squash is tender (about 3 minutes). Stir the squash a few times to keep it from burning. Add rosemary, lemon zest, a pinch of salt and several turns of black pepper, stirring to combine. Season to taste with additional salt and pepper, then take the skillet off the heat.