Liu Bei has a high degree of trust in Zhao Yun. Zhao Yun began to follow Liu Bei when he was young. At that time, Liu Bei had no influence, but Zhao Yun followed him for so many years. During this period, he saved Liu Bei and Liu Chan. If nothing else, just saving Dou, how could Liu Bei not value Zhao Yun? It was out of trust in him that Liu Bei entrusted him with the affairs of the inner room and also entrusted Zhao Yun with the safety of Kyoto. On the bright side, although General Yi Jun is a praetorian guard, he can't make meritorious service in killing the enemy on the battlefield, but in fact such a position is only suitable for people who trust him very much, because the praetorian guard in Kyoto has great power.
Unlike Zhao Yun, Huang Zhong is an expatriate general. Zhao Yun's task is to protect the security of the royal family and Kyoto, while Huang Zhong killed the enemy before the war, which is more dangerous and has direct military merits. Moreover, at that time, on the battlefield of Dingjun Mountain, Huang Zhong defeated Cao's generals and killed Xia. It was this battle that gave Liu Bei the upper hand and proclaimed himself emperor in Hanzhong. Liu Bei naturally can't give a small reward for such a great contribution. General Zheng is just suitable for such a general who killed the enemy before the battle to show his attention to Huang Zhong. Zhao Yun didn't make much military achievements on the battlefield because of his functional reasons, so he couldn't compare with Huang Zhong. Because of this, as a superior, even if Liu Bei is close to Zhao Yun's heart and trusts him again, Liu Bei can't put Zhao Yun above Huang Zhong when he needs military strength when he first ascended the throne.
In fact, from other aspects, Zhao Yun's responsibility is important, but it is directly proportional to the safety, treatment and danger of often going to the battlefield, which makes people convinced. Besides, Huang Zhong's brilliant military achievements are there, and Liu Bei naturally cannot chill the hearts of all the soldiers. In fact, Zhao Yun's treatment is also good. Unless Liu Bei has great trust in him, how can he be in charge of the guards in Kyoto?