Roronoa Zoro had 5 swords throughout the series with one getting destroyed later on in the series. He was the first crew member that Luffy recruited. He was famously known as 'Pirate Hunter Zoro' as his profession before becoming a part of the Straw Hats crew was that of a bounty hunter.
Currently Zoro is a master of the Three Sword Style, a technique that was made in his village but he dreams of becoming one of the strongest swordsmen in the world.
Sandai Kitetsu is a part of the Wazamono blades also known as the Grade Swords. This sword was first seen used by Zoro during the Loguetown Arc after he senses some sinister energy coming from it. It was then revealed that this sword is a cursed one and is quite difficult to control due to the fact it has a thirst for blood and it can bring upon terrible death for the wielder.
Luckily Zoro has good control over it and doesn't feel the side effects of weighing the swords. He even imbued it with haki to make it stronger and durable. This was the one of his first blade in the series.
Yubashiri is another blade that we see Zoro wielding during the Loguetown Arc. After testing his courage against the Sandai Kitetsu curse, Ipponmatsu was extremely impressed by him and decided to gift it him Yubashiri. This sword is the total opposite of Sandau Kitetsu and is quite easy to control. Despite it being very light, it's edge is very sharp but Zoro didn't have trouble getting used to it.
Zoro lost Yubashiri during the Enies Lobby Arc when he was fighting against Shu. The sword was put to rest after Thriller Bark Arc and Zoro even gave it a funeral.
This was the first sword that we see in Zoro's mouth during the first episode of One Piece. It was forged by Shimotsuki Kozaburou, a swordsman from Wano City. This sword originally belonged to Koushiro, the Dojo master of Zoro from the Shimotsuki Village and was actually inherited by his daughter Kuina.
But after her death, Zoro took the sword so that he is able to carry the promise he made to Kuina and become the best swordsman in the entire world. This sword doesn't have a particular nature and is very easy to control. It originally belonged to the 21 O Wazamono grade swords which are considered to very strong.
Enma was also forged by Shimotsuki Kozaburo and it is an incredibly powerful sword. It also originally belonged to the 21 O Wazamono grade swords. This sword was wielded by Kozuki Oden. Enma is the only known sword that can injure Kaido and has been passed down through generations in the Kozuki family. This is what makes the sword interesting and it harnesses quite a strong power.
When Hiyori sees one of Zoro's swords and identifies it as Shusui. She then tells Zoro that if his sword is Shusui then he should respectfully return it back to the Land Of Wano. In return she offers a replacement of the sword with a sword that has been passed down in her family for generations, Enma- the flaming blade and the only weapon known ever to injure Kaido. Thus, Zoro acquires Enma.
Shusui is also a part of the 21 O Wazamono grade swords and it was also forged by Shimotsuki Kozaburo. Using this blade Ryuma was able to slice off the Dragon's head. After his death, it was under the possession of a zombie and then came to Zoro who defeated it and the zombie offered it to him as a sign of respect for his proficient swordsmanship. The sword has a permanent coat of Armament Haki.
It is the only known black blade in the One Piece series so far. It is incredibly powerful and it can swallow up slashes from Wado Ichimonji and Sandai Kitetsu easily. It is known for its hardness and durability.
A. Shusui was Zoro’s strongest sword.
A. Sandai Kitetsu is Zoro’s weakest sword.