You've learned to over ride the truth of a zone of truth with your own. Upong entering a zone of truth you may cast this spell to override it and turn it into a zone of lies. The caster of the zone of truth must make a arcana check equal to your spell dc to determine that his zone has been overwritten. On a failed save the zone of truths caster will believe that you are telling the truth willingly and that you failed the saving throw against the zone of truth. On a succesful save the target will notice that their spell has been corrupted and may respond accordingly. While within the zone of lies a creature can't speak a deliberate truth.