Oda could've just let Zoro stay down with nothing more for the arc.
But just one chapter later he is already doing something else with Zoro, that might be related to Enma, because of King of Hell.
I think because Zoro passed Enma's test by giving it all, Enma might be talking to Zoro.
Kinda like bleach swords.
But this could be all wrong, and it could be just a gag that Oda is making someone look like the Grimm Reaper because Zoro is fucked up.
Anyway, Oda chose to make Zoro relevant again, instead of just letting him stay off screen for the rest of the arc now that his fight is done.