Literal translation
he is looking for hairs on an egg
Meaning
he's nitpicking, splitting hairs
Explanation
The expression names someone excessively fussy, bent on finding a flaw or a detail to criticize at all costs, even where none plainly exists. Literally, cerco de péu sus un iòu translates as he's looking for hairs on an egg: an egg's shell is perfectly smooth, naturally free of any hair, so that trying to find one is an absurd, doomed endeavor, short of inventing what one is looking for out of thin air. The image matches almost exactly the French chercher la petite bête, sharing the idea of fussiness pushed to the point of the ridiculous, applied to matters that do not call for it. The register is familiar, often used with exasperation toward a colleague, a relative, or a superior whose perfectionism slides into sterile nitpicking, needlessly delaying or complicating a task or decision that could otherwise be settled simply.