The owner of xiaosun Xiaozhang's ancient things inferred

Mr. Sun and Mr. Zhang are fellow archaeologists of Lao Li.
One day, old Li took an old thing to test the two. Neither of them could verify who the old thing was.
Lao Li told Mr. Sun's owner's surname, told Mr. Zhang's owner's name, and wrote the following people on the paper, asking them who is the owner?
Zhao Kuo Zhao Yun Zhao Peng
Shen Kuo, Shen Wansan
Yue Fei Yue cloud
Zhang Fei Zhang Liang Zhang Peng

Sun said: I don't know, and I certainly don't know!
Xiao Zhang said: I didn't know either. Now I know what Xiao Sun said!
Sun said: Oh, I know.