Complex sentence: Cao Cao strongly disapproved He Jin's idea as he felt that the best way to deal with the eunuchs was to execute their chief and that recalling external forces into the capital would result in the plan being leaked out.
Split into simpler sentences: Cao Cao strongly disapproved He Jin's idea because he felt that the best way to deal with the eunuchs was to execute their chief. He also remarked that summoning external forces into the capital would result in the plan being leaked out.