Korean Four-Character Idioms
막상막하
莫上莫下
Word for word
“neither above nor below”
What it means
Neck and neck; too close to call.
When you'd use it
A close match or two equally good options.
Example
두 팀 실력이 막상막하라 결과를 모르겠어.The two teams are neck and neck — no telling who'll win.