Toei is going to make an episode out of this
My personal headcanon for Zoro involves him literally slipping into temporal portals and appearing briefly in other moments/places through history, before accidentally stumbling back into his actual timeline.
Zoro watching the pyramids get built
Zoro in the Battle of Waterloo
Zoro being responsible for at least half of the unexplained deaths in the Bermuda Triangle after attacking random planes that started firing on him
Zoro never talks about his past, we have no idea what this man has seen getting lost.