Preheat oven to 375. In a food processor or blender, process pretzels into crumbs; add sugar and pulse until combined. Add butter and mix well. With machine running, add 2 tablespoons of limeade concentrate; process until well-mixed.
Spoon mixture into an ungreased 9-inch pie plate. With back of a spoon, press mixture firmly into bottom and up sides of pan to form a pie shell. Bake until set, about 10 minutes; place in freezer for 10 minutes until cool.
Meanwhile, in an electric mixer, combine ice cream, remaining limeade concentrate, tequila, liqueur and lime zest; mix until just blended. Spoon ice cream mixture into cooled pie shell. Freeze for 2 hours before cutting into 8 pieces.
Assemble, Blend, Process