Meanwhile, in an electric mixer with the wire whisk attachment, beat the egg yolks and lime zest at high speed until very fluffy, about 5 minutes. Gradually add the condensed milk and continue to beat until thick, 3 or 4 minutes longer. Lower the mixer speed and slowly add the lime juice, mixing just until combined, no longer. Pour the mixture into the crust. Bake for 10 minutes, or until the filling has just set. Cool on a wire rack, then refrigerate. Freeze for 15 to 20 minutes before serving.