With the viz out, this is how it looks. In Enma's initial description, it was mentioned it's property relied on exuding the wielder's haki on it's own
And thus Zoro trained to control the blade in order for him to exude his haki on Enma at will. Something to note is that ever since he trained with Enma, we never really saw him using hardening, even after he had a better control of the blade
I think it might be because in Zoro's training, he aimed at using the minimal amount of haki necessary to gradually tame the blade
Basically his way to gradually exhibits more and more haki the greater his control over Enma became
And i think Zoro managed to tame Enma at the minimal level, meaning that he can now exudes his haki on Enma at will. However he can't properly control the amount
Which is the reason of this statement
He wants to unleash Enma "a bit more", but why just a bit ? Because if he isn't careful enough, Enma might suck out more haki than he wants
And thus Zoro trained to control the blade in order for him to exude his haki on Enma at will. Something to note is that ever since he trained with Enma, we never really saw him using hardening, even after he had a better control of the blade
I think it might be because in Zoro's training, he aimed at using the minimal amount of haki necessary to gradually tame the blade
Basically his way to gradually exhibits more and more haki the greater his control over Enma became
And i think Zoro managed to tame Enma at the minimal level, meaning that he can now exudes his haki on Enma at will. However he can't properly control the amount
Which is the reason of this statement
He wants to unleash Enma "a bit more", but why just a bit ? Because if he isn't careful enough, Enma might suck out more haki than he wants