as you can see only Enma Is the source of that strange haki.
Zoro cannot use his mode without Enma.
You guya don't give credit to Enma like Kaido did.
The "strange" Haki Kaido is referring to is Zoro's excessive CoA output.
Zoro was holding his CoA back in an attempt to prevent Enma from stealing it all. Hence, he needed to release more CoA of which Enma would forcibly draw more than his other swords.
We know exactly what Enma does:
It simply draws out the user's Ryuo by itself and as a result, cuts more than required. It doesn't give you magic Haki or transfer special powers to your other swords.
If you're releasing 40% of your CoA onto each sword, Enma will take 80% for example. That's why Zoro realised he needs to be releasing 100% always onto every sword. There is little difference between a mastered Enma and swords of the same rank - hence why the art on Zoro's attacks changed once he awakened KOH.
Previously, Enma would be the only sword with a strange aura during every attack - that was a sign that it was drawing more CoA than Zoro's other swords. And now every sword is smoking, indicating each sword is being provided with the same amount of CoA, which is 100%. Enma can't draw out more than 100% of your Haki, it's just no one fights using 100% of their Haki because it'll kill them. No one but Oden and now Zoro, whose body will adjust to this technique.
Why do you think Enma and Ame no Habakiri inflicted equal scars on Kaido? Why do you think there's no longer any difference in art style between Enma and Zoro's other swords? Because Enma is not a magic sword. KOH can be done with any weapon.