User blog comment:Miskos3/Fairy Tail Chapter 506: The Broken Bond, Review/@comment-25111584-20161017131428/@comment-1776824-20161018172348

If you google tandem, it quite literally means alongside each other or together, and this is exactly what Gray is doing. Gray is simultaneously converting and shaping ice into devil slaying ice. The Zero no Haken is the prime example of this.