Wrong.
Zoro's normal haki output = Oden normal hakk output.
Koh uses Zoro using overwhelming haki. A feat Oden can perform but doesn't normally use.
The manga stated the enma came to test Zoro.
The state enma is presented to us in the scene is the test, control enma while using overwhelming haki. The smoke/flames means there is overwhelming haki added to enma.
In the next scene, Zoro said you mean to tell me even with so much haki drained Oden could wielded you as light as a feather.
Zoro talking about Oden using enma while it's in its current state with smoke/flames and overwhelming haki.
To pass the test Zoro had to prove he could use enma easily even with so much. He did, he just turned that test into his own unique sword style.
During the Oden flashback we never saw smoke/flames on the sword which means Oden doesn't normally use that amount of haki.
Oden cut Kaido with both swords. Enma doesn't affect the user other swords.