Enma drew out ridiculous amounts of Haki. Without it he'd have lost to King and Kaidou would have killed him.
When Zoro allowed it, yes, happened once.
At cost of haki reserve depleting faster.
Without Enma, Zoro would fight for longer.
Enma literally did nothing for Zoro against either King or Kaido.
It dragged him down vs King as King himself said so.
VS Kaido did nothing as well, I dont remember a scene where Kaido would have killed Zoro if he had no Enma, lol.
Zoro's rooftop performance is irrelevant of Enma. The one time it drew lots of Haki, Zoro missed so nothing came of it.