The claim that Zoro needs Enma to unleash his haki fully is a rather absurd one. Enma simply forces Zoro to give up as much Haki as it wants. It was never implied nor stated that Enma allows its users to give that Haki to anything other than itself. It's like a vacuum, in that it takes, but it's never gives back. If you believe otherwise, post the panels, or concede on this point.
If we bring such line of thinking to it's logical conclusion, then Zoro would not only allow Enma to continue sucking Haki, but then he'd need to pull that Haki out from the blade, and then flow the Haki through the two other blades as well with the same amount of Haki, all the while STILL fighting against Enma's suck game as well, which would be the best showing of Haki control in the whole series. And now he does it casually with little to no display of struggling to do so, and in turn would make Zoro's feat of mastery Enma to such a degree way more impressive than it actually is, when in fact this is not the case.
To further demonstrate why this assumption is utterly false, I will go into the reasons within the story why this would be actually an antithesis to Zoro's "arc" in Wano, as non-substantial as it may be.
1. If Zoro needed Enma to take Haki and diverting the Haki Enma would be sucking to his other blades, then by logical deduction we can come to the conclusion that he is withholding Haki that Enma could be taking, which in turn would mean he's still limiting Enma, which goes against the conclusion Zoro reached near the end of the King fight, to simply relinquish everything he has to Enma voluntarily.
2. If he was limiting the amount of Haki he was giving to Enma, not giving his all to it, then by extension he is still limiting himself as well, when the main theme of the fight was for Zoro to realize that he shouldn't limit his Haki, which in turn means that he should limiting his will (as Haki = willpower) to simply use his dream as a means to an end for Luffy. Have any of you noticed how King paralleled Zoro, in that prior to Zoro's epiphany, they both prioritized making their captains Pirate King over anything else, limiting themselves to merely be their captains' guns, and only when Zoro came to the realization that he didn't need to prioritize Luffy's dream over his own, nor vice versa, did he coincidentally unlock Conquerors' coating as well, and proceeded to outright humiliate King in not only the fight, but also in their purpose in life, as Zoro mentally at that moment became more than what King will ever be and he himself was prior to this revelation, a servant, and renown himself as the King of Hell, who had his own dream to fulfill. That's also why he mentions both Kuina and Luffy, as he now holds his promise to Kuina to become the World's Strongest Swordsman at the same value as his promise to Luffy to make him King of the Pirates, and Enma has stopped acting up since this event has transpired.
Tl;dr: Enma simply forced Zoro to stop holding his Haki back. He didn't need Enma to do so in the 1st place as it was a mental obstacle rather than a physical one, and Enma has never shown to act on its own accord post-Wano, displaying that Zoro is willingly unleashing as much Haki as he possibly can.