Combine lemon zest and vodka in an airtight container. Cover and place in a cool, dark space, shaking the container to redistribute the lemon zest once a day for 5 days.
Pour milk and sugar into a large pot and bringing to a low boil, stirring often, until the sugar has dissolved.
Remove from heat and allow milk mixture to cool to room temperature. Slowly strain vodka mixture into the milk using a sieve. Discard the lemon zest.
Pour limoncello into a capped bottle and place in the freezer to chill for 1 hour.
