Complex sentence: Cao Cao wrote a memorial to Emperor Ling, in which he defended Dou Wu and Chen Fan, pointed out that the court was full of corrupt officials, and mentioned that advice from loyal subjects was not being heard.
Split into simpler sentences: Cao Cao wrote a memorial to Emperor Ling to defend Dou Wu and Chen Fan and point out that the imperial court was full of corrupt officials. He also mentioned that advice from loyal subjects was not being heard.