Over low heat, combine heavy whipping cream, half-and-half, sugar, lemon zest; allow to simmer, stirring, until sugar is dissolved. This will take roughly 5 minutes.
Remove cream from heat, cover the pan, and steep for 5 minutes.
Put the cream back on the heat, allowing it to simmer.
Place egg yolks in a bowl & beat until smooth. Gradually add a little of the warm cream mixture to the eggs (up to roughly 1/2 c., a couple of tablespoons at a time) bringing them up to temperature without cooking them.
Combine the warm egg mixture with the large pot of cream.
Add the lemon juice and vanilla extract; cook/stir until the mixture coats the back of your spatula. This will take 3-5 minutes.
Transfer to a freezer-safe dish and freeze overnight.
The next day, add the lemon ice cream to a mason jar. Slowly pour Ale-8-One over the ice cream, making a float. If needed, add more as you eat. Top with whipped cream.