1. Combine wine, sugar, lemon zest, vanilla and cinnamon stick in a wide saucepan. Bring to a boil over high heat, stirring just until sugar has dissolved. Reduce heat to medium and simmer for 2 minutes to blend flavors.
2. Peel pears and cut in half lengthwise. Use a small spoon or a melon baller to scoop out center core and seeds. Working quickly, gently lower pears into poaching liquid. Place a clean kitchen towel over pears to keep them in liquid. (Be sure all pear halves are submerged. Add water or cook in batches, if necessary.) Simmer until pears are tender when pierced with a knife, 15 to 25 minutes, depending on ripeness. Use a slotted spoon to transfer pears to a large bowl.
3. Raise heat to high and bring poaching liquid back to a boil. Boil rapidly until liquid has reduced and thickened slightly, 20 to 25 minutes. Cool slightly, remove cinnamon stick and pour liquid over pears. Serve warm or cover, refrigerate and serve chilled.