Mao did not have the ability to prosecute Deng, not did not want to. He can deprive Deng's right to work, but Zhou and his camp would allow Mao to kill Deng.
Zhou was a real existence during the 27 years after the establishment of New China. He controlled the excecutive team - no one could even sway, not to say clapse, he post. Gao Gang, Liu Shaoqing, Lin Biao, all tried with backup of Mao, but none of them ever successed. Lin almost, but finally ...