labor of Hercules

A job, task, or activity that requires a huge amount of effort, energy, or physical strength. Sometimes used ironically or hyperbolically. But getting enough votes to pass the controversial legislation may prove to be a labor of Hercules. Sometimes it feels like finding a good burger that isn't the price of a sirloin steak is a labor of Hercules. It will be a labor of Hercules for them to dethrone the former champions in this year's Super Bowl, but they certainly have a shot.

a labour of Hercules

a task requiring enormous strength or effort.

In Greek mythology, Hercules was a man of superhuman strength and courage who performed twelve immense tasks or labours imposed on him as a penance for killing his children in a fit of madness. After his death he was ranked among the gods.