殚精竭虑 (殫精竭慮) dān jīng jié lǜ

dān jīng jié lǜ set phrase to exhaust one's thoughts and ingenuity; to think something through thoroughly; to rack one's brains; to leave no stone unturned
Domain: Idiom 成语
Notes: (CC-CEDICT '殫精竭慮'; Guoyu '殫精竭慮')