to waste one's efforts on a scheme; to plot in vain; to exhaust one's ingenuity to no avail

To expend a lot of effort and energy; to go through a great deal of trouble.

to waste one's efforts and mental energy; to go to great trouble to no avail

to waste one's time and effort on calculations or schemes to no avail; to rack one's brains only to end up with nothing

to waste one's energy or thoughts on a futile effort; to scheme or worry for nothing