~てはしない form grammar


I've seen this a few times and always just been guessing the meaning. I have
this dialogue were 勝てはしない is said. Is ...てはしない used for emphasis? Saying that
winning can't be done?

I'm just curious why I never read about this grammar in my books or anywhere
else. Is it like saying it is impossible? Like 勝ち得ない or something. I'd like
your help. Dialogue under with my attempted translation.

深海王を狩るつもりならやめておけ If your intention is about to hunt the deep sea king leave it
for me

深海王? The deep sea king?

ヒーローごときが束になっても勝てはしない Even if heroes bunch together we can't win

