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.
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.
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.
Whether you liked the ending or not, it is how the author imagined the post-Demon Slayer world and in it, Zenitsu never becomes a Hashira.
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 Clap and Flash—Godspeed is the most powerful of Zenitsu's derivations of the Thunder Breathing first-form technique.
1. Gyomei Himejima. Gyomei Himejima, the Stone Hashira, is the strongest Hashira in the Demon Slayer corps in terms of strength and swordsmanship. He is the only person who uses spiked flails and an axe instead of standard swords to kill demons.
Despite her petite appearance, Mitsuri Kanroji has a special muscular composition that makes her muscles eight times denser than an ordinary human's. She is also more flexible than the other Hashira. These two strengths balance out her being the slowest runner out of all the Hashira.
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.
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.
3 Can't Beat: Nezuko
Her strength and speed when she's embracing her new demon abilities are pretty impressive, and she'd likely give Zenitsu a run for his money if they were to fight.
3) Zenitsu Agatsuma
If he could, Rengoku would win simply because Zenitsu cannot perform Godspeed more than twice. Since Zenitsu only knows the first form, Rengoku would know what to expect and accordingly counter his moves, taking him down in the end.
Zenitsu trained under the former Thunder Hashira, Jigoro Kuwajima. Under Jigoro's strict training, Zenitsu only mastered the first form of Thunder Breathing.
Abilities and Powers. Overall Abilities: As a Hashira of the Demon Slayer Corps, Nezuko is a very powerful and skilled swordswoman and combatant.
Jigoro was the instructor of Zenitsu and Kaigaku as the former Thunder Hashira.
8 Shinobu Kocho, The Insect Hashira
That being said, she's arguably the weakest Hashira when it comes to pure strength. However, brawn is not the only way to determine power in Demon Slayer.
Shinobu Kocho's tragic backstory is one of the most heart-wrenching in Demon Slayer. She and her sister, Kanae, were orphaned at a young age after their parents were killed by a demon.
Unfortunately, many fan-favorite characters didn't survive in Demon Slayer, and the Hashira certainly weren't an exception. Demon Slayer's nine Hashira are humanity's last line of defense against the vicious demons that rule the night.
1) Shinobu Kocho
The Insect Pillar of Demon Slayer Corps, Shinobu is undeniably the smartest individual.
Demon Slayer's Tengen Uzui is considered to be one of the weakest Hashira due to almost losing this fight, but the fact is that Tengen only looks weak when compared to the most overpowered Hashira.
1) Kyojuro Rengoku
Kyojuro Rangoku is the Flame Hashira that was loved by the entire fanbase. His enthusiasm and an unwavering sense of justice enabled him to become the man that he was. Unfortunately, Rengoku was killed by Akaza, the Upper Moon 3.
NO. It's his subconscious mind that helps him fight. When he fainted out, his subconscious mind takes over( something like semi-hypnotic state) and unleashes the lighting breathing. Consciously he is not confident enough.
Among the current generation members, Shinobu and Zenitsu are the fastest characters in the series. According to the Upper Moon 2, Shinobu was the fastest opponent he had faced and was unable to react to her attacks due to its speed.
One major part of why Zenitsu is scared of demons has to do with his Breathing Style Form mastery. Zenitsu uses the Thunder Breathing Style, but has only mastered the First Form for combat use.