Heat oven to 375°F. In food processor bowl with metal blade or blender container, process pretzel twists until crumbs form. Add sugar; process with on/off pulses to mix. Add margarine; mix well. With machine running, add 2 tablespoons of the limeade concentrate, processing until well mixed. Place mixture in ungreased 9-inch pie pan. With back of spoon, press mixture firmly in bottom and up sides of pan.
Bake at 375°F. for 5 to 7 minutes or until set. Place baked shell in freezer or refrigerator for 10 to 15 minutes to cool.
Meanwhile, in clean food processor bowl with metal blade or large bowl for electric mixer, combine ice cream, remaining limeade concentrate, lime peel, tequila and liqueur; process or mix just until blended. Spoon into cooled baked shell. Freeze 2 hours or until firm.