hard tier
Look at the pencil marks in the two highlighted cells, both in the same column. Digits 5 and 7 only show up as candidates in these two cells anywhere in the column — even though the marked cell's pencil marks show another number too.
Since 5 and 7 have to occupy these two cells (in some order), nothing else can go in either one — so every other candidate can be crossed off the marked cell, narrowing it down to just 5 or 7.