Z moves are used with any move of the same type as the Z-crystal, so with Normalium Z, you would get Breakneck Blitz as Z-fake out, which wold have the same effects as fake out, but with a little extra thanks to the Z crystal. As to it only being able to be used on the first turn, it is likely, as Z-moves normally hold on to a lot of effects of the original move, but the Z-crystal might make the move better by taking that part away. I don't have the game, but will soon, and this is just a hypothesis.
source: knowledge