Using a vegetable peeler, remove all of the zest from 3 of the lemons in 3- to 4-inch-long strips. Set the lemons aside.
Combine the lemon zest, cream, milk, sugar, and salt in a large saucepan. Bring to a simmer over medium heat, stirring occasionally to dissolve the sugar, about 5 minutes. Remove from the heat. Let steep at room temperature, stirring occasionally, for 20 minutes.
Squeeze 2/3 cup juice from the reserved lemons (juice the fourth lemon, if necessary). Stirring constantly, pour the lemon juice into the cream mixture in a slow stream. Stir in the vodka.
Strain the mixture through a fine sieve into a 4-cup glass measure (or any container with a spout for easy pouring), pressing on the solids to extract as much liquid as possible. Divide the mixture among eight 3-oz. pop molds or wax-lined paper cups. Freeze until just barely set, 5 to 6 hours. Insert craft sticks and freeze until completely set, about 2 hours more. When ready to serve, unmold or peel off the paper cups.
The pops can be frozen for up to 3 days.