Place sugar, water, and zest in a small saucepan over medium heat. Bring to a boil, let the sugar dissolve, and boil for one minute. Take off of the heat, and add in the lemon juice. The syrup will keep in the fridge for a few weeks (if it lasts that long).
Mix any leftover syrup with club soda or vodka. Or, make lemonade with water, syrup, and lemon juice.