In a bowl, combine the lime juice, zest, water, condensed milk, and tequila and stir well. Divide the salt evenly into the bottom (later, it will be the top) of each of six 4-ounce frozen pop molds. Pour the margarita mixture into each mold, leaving about 1/2 inch headspace for the liquid’s expansion in the freezer. Freeze for 6 hours, until solid.
To release an individual pop, rotate it under a stream of running warm tap water for about 30 seconds. Never tug on the stick! Keep running it under water until the pop can be pulled out gently. (Should this fail, eat your pop from the mold with a spoon.)