Cero is cool, but not super cool yet.
I mean, one click on the verb creates a small ball infront of the user, and a sec later the cero is fired (like usual) and uses normal Rei, and stops after it hits one person.
However, once you master "first stage" of the Cero, you can click, and when the ball is formed, click again and the ball will grow a bit more, and the Cero will be stronger, twice the Rei, and goes through the first target, but stops when hitting the 2nd. After it hits the first target, the 2nd target gets hit by a Cero that is as strong as level one Cero.
After mastering that one, you can click a third time so the ball would grow, taking tripe the Rei, and tripe the attack on the first target, twice the attack on the 2nd target, and stops with normal attack power on the 3rd target.
What's the catch? Each time you click Cero again to charge the next level, it takes another second, giving the target time to escape, also it takes much more Rei. However the first drawback can be taken off if you have some sort of a binding spell, like, if your the tentacle arrancar, or if you have someone with a bind spell helping.