That would be a tough nut to swallow

This clever congruent conflation is a blend of “tough nut to crack” and “bitter pill to swallow”, both referring to hard things to do.  Both also contain four words, and both involve actions.   And of course a tough nut is always hard to swallow,
right?  A big shout out to Susan E for sending me this one that she heard her husband utter last week.