CAM ЧЁРТ (НИ ОДИН ЧЁРТ, И ЧЁРТ) не разберет, не поймёт collNPnomsing onlysubj) no one (will understand sth. ), it is absolutely impossible (to make sth. out)
the devil himself (couldn't figure sth. out (would be hard put to know sth.etc)).
«Сам чёрт не разберёт, кто тут плохой, кто хороший...» (Гинзбург 2). "The devil himself would be hard put to know who's good and who's bad around here" (2a).