My friend’s name is “Isaiah Lee” and he wants to know if these characters(以賽亞) are appropriate for his Chinese name?

Well, Isaiah Lee is translated in Chinese as 以赛亚·李. In my humble opinion, if your friend wants to have a name looks and sounds more like a Chinese name, then Li Zeyan, or 李泽彦 in Chinese, could also be an option.

李 is a major surname in Mainland China. The founder of Tang Dynasty, a well-known Chinese dynasty, was Li Yuan, or 李渊 (566–635) in Chinese. There are many people who share this surname, for instance, Li Xian, or 李现 in Chinese, an actor from mainland China. Li Chen, or 李晨 in Chinese, an actor from mainland China.

Here is a picture of Li Xian.

Here is a picture of Li Chen.

The Chinese character 泽 could mean favor and beneficence. And there are people whose generational name is 泽, for example, Li Zexiang, or 李泽湘 in Chinese, a professor from Hong Kong University of Science and Technology and Li Zefeng, or 李泽锋 in Chinese, an actor from mainland China.

Here is a picture of Li Zexiang.

Here is a picture of Li Zefeng.

The Chinese character 彦 could mean people of virtue and ability. And you could find 彦 used as the given name in names of other people, such as, Huang Yan, or 黄彦 in Chinese, an actor from mainland China and Shaun Tam, or 谭俊彦 in Chinese, an actor from Hong Kong.

Here is a picture of Huang Yan.

Here is a picture of Shaun Tam.