Zenitsu managed to master only the first form of Thunder Breathing. His training was cut short before he could master the other forms, although the first one serves as the basis for all of the others.
This mastery allowed Zenitsu to form a Seventh Form of Thunder Breathing that is unique only to him: Honoikazuchi no Kami. While this move might seem similar to Thunder Breathing's First Form, the speed and power of this technique are on a whole new level.
So in a nutshell, Zenitsu wasn't able to master the other five forms, but later in the Infinity Castle Arc, during the battle with Kaigaku, Upper-Rank Six Demon, he created a Seventh Form: Flaming Thunder God.
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.
Thunder Breathing has 6 standard forms in total, with the first form said to be the foundation for all the other forms. However, Zenitsu Agatsuma developed a Seventh Form in order to stand on equal ground with Kaigaku, his former senior disciple under Jigoro who had become the Upper Rank Six of the Twelve Kizuki.
Thunder Clap and Flash—Godspeed is the most powerful of Zenitsu's derivations of the Thunder Breathing first-form technique.
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.
Zenitsu is definitely faster but Tanjirou is more tactical and more versatile. Tanjirou could lose if he has no idea what Zenitsu can do, but if he does he can easily anticipate. Currently in the manga, Tanjirou is definitely stronger.
Why Zenitsu could not become a Hashira in Demon Slayer. Fans have wondered whether Zenitsu ever got to realize his dream of becoming a Hashira at all. Unfortunately, the answer to this question would be, no, he did not. Zenitsu, along with Tanjiro and Inosuke got way stronger than average corps members with training.
172.1 Km/h Whenever he performs his thunderclap And flash move.
The eccentric and flamboyant Tengen Uzui is the current Sound Hashira. This Breathing Technique gives him echolocation and other advanced hearing abilities.
That's the thing about Zenitsu. He doesn't realize how strong he is because his anxiety holds him back. While unconscious, he can have a clear head and fight back, giving Zenitsu an edge over his fellow slayers.
Zenitsu doesn't realize his own strength
He ends up making it out of the Final Selection alive, but he's not happy about it.
To sum it up, it is possible for Zenitsu to fight without fainting and it has been shown clearly in the manga. While he only perfected the first form, he trained hard enough to create a new form that didn't exist before.
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.
But, comparing the two characters in their best forms, Zenitsu might be just a tad bit faster owing to his Godspeed move.
Those who have read the manga know that Tanjiro's powers grow exponentially towards the end of the series. His skill and overall combat abilities could be compared to that of a Hashira's. That being said, there is absolutely no chance for Tanjiro Kamado to be able to beat Kibutsuji Muzan.
Unfortunately, he retired at the age of 35, when he lost his right leg in a fight with a demon. Since then, he devoted his time to teaching the next generation of demon slayers, most notably, Zenitsu Agatsuma, who lovingly called him "grandpa".
After the deaths of Daki and Gyutaro, Kaigaku was promoted to become Upper Moon Six of the Twelve Demon Moons due to his power and confronted Zenitsu as a rematch he always desired.
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.
2) Tanjiro Kamado
With Sun Breathing, which is regarded as the paramount of all Breathing Styles, Zenitsu will have a hard time subduing Tanjiro and will be defeated by the latter in no time.
3) Zenitsu Agatsuma
Zenitsu, with his insane strength and lightning speed, can eliminate every Upper-Rank Demon in 1v1 except Upper Moon 1, and Muzan because in terms of strength they are more formidable than him.
However, in front of Giyu, Zenitsu is a much inferior opponent. He is just a newbie, while Giyu possesses greater strength, immense speed, and superior combat experience. If Giyu fights Zenitsu, the latter will lose miserably.