There are six forms, but Zenitsu could only learn the first form said to be the basis for the others yet he honed it to where he could fight against several strong demons. He later created a seventh form and defeated his former senior who had become the Upper Rank Six of the Twelve Kizuki.
With his master gone, Zenitsu can no longer learn the remaining five forms. Therefore, during his fight with Kaigaku, an Upper Moon Six, he created a 7th form.
However, as every Demon Slayer affiliated with a Breathing Style develops certain forms which give them an advantage in combat, Zenitsu could only learn the first form of Thunder Breathing: Thunderclap and Flash.
Zenitsu creates his own form called Seventh Form: Honoikazuchi Nokami. Through this form, he is able to conjure a creature akin to a dragon that breathes thunder and fire. When combined with God Speed, his power and strength increase, giving him the ability to defeat demons like Kaiju, from the Upper Moon Six.
172.1 Km/h Whenever he performs his thunderclap And flash move.
Thunder Clap and Flash—Godspeed is the most powerful of Zenitsu's derivations of the Thunder Breathing first-form technique.
After Muzan was defeated, all the demons he created also perished immediately, so there was no point of a Demon Slayer corps anymore. As a result, Zenitsu did not get to become a Hashira even after becoming strong enough to bie one.
Nezuko Kamado
Zenitsu also protects Nezuko multiple times when she is in danger, evident during Zenitsu's first meeting with Inosuke Hashibira and the battle against Enmu in the train. Eventually Zenitsu and Nezuko would marry and start a family as evidenced by their descendants.
As he only knows one move, it would become easy for the latter to counter his attacks and get a better chance to land a strike that would end his life. However, if Zenitsu masters all the forms of his Breathing Technique, he would definitely beat him in speed and strength.
There are six forms, but Zenitsu could only learn the first form said to be the basis for the others yet he honed it to where he could fight against several strong demons. He later created a seventh form and defeated his former senior who had become the Upper Rank Six of the Twelve Kizuki.
How fast is Zenitsu?? I mean it's difficult to tell, but at least 750 mph since he can break the sound barrier.
The reason for this is pretty simple. Zenitsu wasn't able to master the other 5 forms. He never wanted to learn any breathing techniques. or fighting techniques, nor he wanted to join the Demon Slayer Corps. He was forced, not in a bad way, to train because his master, Jigger Okuwajima, saw potential in him.
Thirteenth Form of Sun Breathing in Demon Slayer
It involves a combination of all existing Sun breathing techniques — but performed in a consecutive manner. This technique's primary purpose is to slash all the twelve vital organs of a demon. Each form targets a specific organ. Tanjiro only used it once in the manga.
Sixth Form: Lightningbolt and Flash (Roku no kata: Inazuma Issen) - This move replicates both the first and sixth form of Thunder Breathing in which the swordsman slashes both swords simultaneously in an x formation which is followed by a fast bolt of lightning which stuns and burns the enemy and guarantees no chance ...
Sun Breathing has the second highest number of known techniques of all the breathing styles. It has twelve forms that can all be combined into an extremely powerful thirteenth form. It is second only to Moon Breathing which has sixteen techniques, employed by the Upper Rank One demon Kokushibo.
The adventure and life of a child of a demon and a human. Inosuke Hashibira, a half-demon among demon slayers.
Post-Transformation
Sensing their despair, Doma offered a chance to him and turned both Gyutaro and Daki into demons.
Demon Slayers are known for their strength and bravery in battle, but not Zenitsu. Despite his cowardice, he's one of the strongest in the series.
But, comparing the two characters in their best forms, Zenitsu might be just a tad bit faster owing to his Godspeed move.
Overall, Zenitsu is an extraordinary powerful Demon Slayer capable of singlehandedly bringing down an Upper Rank, which said to be able to overpower 5 Hashira, in 10 minutes, albeit he would have beheaded Kaigaku in a heartbeat if it wasn't for his feelings of melancholy and pity.