Cero ("Sero" spanish meaning "Zero", japanese meaning "Hollow Flash") is a form of attack used by Menos, Arrancar, Visored, and Kakezon. As a standard energy blast, it consists of firing a powerful blast of concentrated spiritual energy at the target. While in most cases it is fired from the mouth, some Arrancars and Kakezon are capable of firing Cero from their hands, fingers and other parts of their bodies.
The power, force, speed, and blast area of the Cero is dependent on the strength, spiritual power, and sometimes skill of the user (i.e., the stronger the user, the stronger the attack), and there are some Arrancar who have even come up with their own variation of Cero. The charging and firing time for Cero also varies greatly, from relatively charging fast to firing it to instantaneously fire one without much charging. Despite the damage it can cause at long range distances, Love Aikawa stated that the damage Cero cause as an explosion is more dangerous when used at close range.
Cero Doble (Sero Doburu; spanish meaning for "Double Zero", japanese meaning for "Heavy Performance Hollow Flash") is a variation performed by Nelliel Tu Odelschwanck, by swallowing her opponent's Cero and returning it back to the user along with her own Cero, making it more powerful. This attack was seen used against Nnoitra Gilga.
While in her child form, Nel is only able to return the Cero fired by her opponent as seen used against Dordoni Alessandro Del Socaccio.
Cero Sincrético (Sero Shinkuretiko; spanish meaning for "Synchronized Zero", japanese meaning for "United Hollow Flash") is a variation performed by Dondochakka Birstanne and Pesche Guatiche. This attack was used against Szayel Aporro Granz. Pesche and Dondochakka charge their Cero simultaneously and combine them, forming a large, swirling sphere. They then fire the combined Cero, launching a multi-colored beam. Although it does not work on him, Szayel Aporro admits that it is a "marvelous technique" and that if they had used it before he had time to analyze their reiatsu, he would have been defeated. However, it does seem to greatly drain Pesche and Dondochakka---both are panting and on the point of collapse after performing it.
Gran Rey Cero
Gran Rey Cero (Guran Rei Sero; spanish meaning for "Grand King Zero", japanese meaning for "Royal Hollow Flash") is a Cero that only Espada are capable of using. It is performed by mixing an Espada's own blood with the Cero. The result is a Cero with a much greater attack power and speed as well as a change of color unique to the Espada. It is also many times more powerful than a normal Cero, capable of disturbing the fabric of space, it also seems to spin like a razor upon release as it compresses and decompresses due to the sheer speed and raw power. It is a drastically potent Cero, used only by the Espada themselves. This attack was first used by Grimmjow Jaegerjaquez in order to incite Ichigo Kurosaki into donning his mask. It is stated by Ulquiorra that using a Gran Rey Cero is one of two things that are forbidden while in Las Noches, as it is so overwhelming that it could destroy the fortress. So far, Grimmjow Jaegerjaquez is the only member of the current Espada to utilize this attack.
Cero Oscuras (Sero Osukyurasu; spanish meaning for "Dark Zero," japanese meaning for "Black Hollow Flash") or more grammatically correct Cero Oscuro, is a black Cero used by Ulquiorra Cifer in his Resurrección form. He also compares it to Ichigo's black Getsuga Tensho. It covers any exposed light into pitch darkness. Though the only Espada shown to utilize this technique so far, Ulquiorra told Ichigo that, "This is an Espada's fully powered Black Cero." Ulquiorra also referred to it as "our Cero." The Cero Oscuras' range is vast, and its attack power is massive. It is powerful enough to shatter Ichigo Kurosaki's entire Hollow mask and critically injure him in the process. It is strong enough to destroy half of the dome over Las Noches. The superior Cero Oscuras is far greater than an average Cero.
Cero Metralleta (Sero Metorajetta; spanish meaning for "Sub-Machine Gun Zero", japanese meaning for "Infinite Ammunition Hollow Flash") is a variation performed by Coyote Starrk while in his Resurrección. By using his right pistol, Starrk is able to fire a barrage of Cero at his opponent. This was first seen used against Shunsui Kyoraku.