In a large pot, heat 2 qt. apple cider, 10 cinnamon sticks, 10 whole cloves, 1 tbsp. freshly grated nutmeg and 1 tbsp. lemon zest until hot but not boiling, at least 10 minutes. Transfer to a heatproof punch bowl (or serve out of the pot) and stir in 12 oz. Calvados.