Can Jiuyin Zhen Jing and Yijinjing learn together?

You can't. According to the website of Life Encyclopedia, Jiuyin Zhen Jing and Yijinjing are different in nature and difficulty, so they can't study together. Yijinjing Shaolin Yijinjing is a martial arts routine with a clear fitness purpose. Jiuyin Zhen Jing is a martial arts secret book written by Jin Yong.