What does the last sentence of Li Hong in Zhen Huan's biography mean "Zheng Boke ..."

Yan Yu, Duan of Zheng Boke, told the story that the Queen Mother loved her youngest son so much that the eldest son in power had to design a plan to lure his younger brother into arrogance and use it as an excuse to crusade.

Duan Yanyu by Zheng Boke is a famous work in Spring and Autumn Annals. This article mainly tells the life-and-death struggle between Lu Yin and his younger brother Duan Shu in order to seize the throne of the country. The design deliberately indulged his younger brother Duan Shu and his mother Wujiang. His younger brother was arrogant, so he wanted to seize the position of the monarch, and Zhuang Gong took this opportunity to punish Duan Shu. Duke Zhuang resented his mother's partiality and moved her to Yu Ying. Later, I regretted it myself. At the suggestion of Uncle Ying Kao, the mother and son got back together.

Confucius didn't think highly of the two brothers. In the Spring and Autumn Period, it was called "Bo", while the younger son was directly called "Duan".

Li Hong's words are for fear that Zhen Xuan will threaten his position when his foundation is unstable, because he loves his youngest son. That's why Zhen Xuan later adopted his youngest son.