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.
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.
1/7 Seventh Form: Honoikazuchi No Kami
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.
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.
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.
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.
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.
Zenitsu speed is nearly that of light. To downgrade it, it is still invisible to naked eye, i.e. more than 51 Mach. Zenitsu speed with his sword skills just blitz Kaminari.
His most useful technique is Honoikazuchi no Kami — a technique created by Zenitsu himself that is incredibly powerful and requires so much speed that Zenitsu's haori is completely ripped to shreds during its execution.
While unconscious, Zenitsu is a force to be reckoned with, but his actual power is discovered when he is awake. While awake, Zenitsu was able to match the upper rank six, Kaigaku. He was also able to keep up with the Demon King, though he was in a weakened state during this battle.
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.
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. In fact, he became one of the very few to even invent a new form of Thunder Breathing. However, his dream of becoming a Hashira was never realized.
When facing Kaigaku during the Infinity Castle arc, Zenitsu debuts his brand new exclusive Seventh Form to Thunder Breathing. With this, Zenitsu finally has more than one tool in his arsenal and has overcome his own personal doubts and fears.
Zenitsu is one of the main characters, and he does stop being a coward in Chapter 143–146, which is hte final arc of the series.
Zenitsu always performs a single form because that is the only form he knows. His attack always start with this positioning, and end result is this way.
1) Inosuke Hashibira
Although Inosuke possesses immense strength and endurance, he's no match for Zenitsu's insane speed and his Thunder Breathing.
10) Zenitsu
He certainly has speed and was able to keep up with Daki during the Entertainment District arc. While some might say that he could one-shot the Upper Moon demon Kaigaku, the demon was nowhere near the level of an Upper Moon since he was not used to his powers.
Tanjiro isn't Faster Than Zenitsu, not at all. He is Strong but Slow. So, Zenitsu Will Probably Chop Him Down to bits before tanjiro even pulls out his sword properly.
Zenitsu Agatsuma is the series' sole Thunder-Breather, although Tengen Uzui's Sound-Breathing is derived from Thunder-Breathing.
Who is Jigoro Kuwajima? Jigoro was a former Hashira who practiced Thunder Breathing, which ended up giving him the title of "Roaring Hashira". Naturally, he was a very powerful demon slayer who successfully killed many demons.
Kaigaku who was strong never be able to learn first form just because his pride he never learned it. The reason he think it is basic form it is useless it is easy to learn for anyone so i won't do it. As we seen tanjiro using this form directly without learning in just first try to decapitate hantengu.
He was formerly the Thunder Hashira ( 鳴 なり 柱 ばしら , Nari Bashira?) in the Demon Slayer Corps.
Comparing Zenitsu before his stay at the Butterfly Estate to Kanao, we'd probably guess that Kanao would defeat him easily in a one-on-one match. But after Tanjiro, Zenitsu, and Inosuke train with Kanao and the others residing at the estate, Zenitsu manages to best her — in terms of speed, at least.
3/10 Did Not: Inosuke Hashibira Trained With Tanjiro But Never Got His Mark. Inosuke, like Zenitsu, spent most of the series traveling with Tanjiro.