殫精竭慮

Simplified: 殚精竭虑

dānjīngjiélǜ ㄉㄢ ㄐㄧㄥ ㄐㄧㄝˊ ㄌㄩˋ

    • to exhaust one's thoughts and ingenuity (idiom) to think sth through thoroughly
    • to rack one's brains
    • to leave no stone unturned

Character by character

Sources