You guys will pull anything out of your ass won't you? Hybrid Kaido does not have tougher skin than Dragon Kaido.
And Zoro's "scar" didn't even bring Kaido down like he wanted. Scabbards did more damage than Zoro. Oden's scar was permanent.
Hybrid Kaido is stronger and tougher than base or dragon Kaido.
When the Scabbards attacked dragon Kaido together they cut him and knocked him down.
But it wasn't enough to open his old wound. Which implies it's harder to create a new scar than it is to open an old scar.
When Zoro attacked dragon Kaido with his dragon twister the attack cut him and knocked him down but didn't create a new scar.
When Zoro attacked Hybrid Kaido with his asura mode attack it cut Kaido and created a new scar. He acknowledge it created a new scar but it didn't knock him down.
You can see from manga facts how much stronger hybrid Kaido is compared to his other two modes.