no matter how hard one tries; even if one stood on one's head
Fixed expression meaning 'no matter what one does' or 'even if one tries one's hardest'. Literally 'even if one does a handstand', it emphasizes the impossibility of achieving something regardless of effort.
See also: 逆立ち
No matter how hard I try, I can't beat him.
I don't think I can solve this problem no matter what I do.