I've never heard anyone pronouncing 人 as zhen (pinyin) in typical of Chinese. I think you should double confirm this with your Chinese teacher...

That's mainly because the tongue position is always the same as in zhi/shi/chi/r

Hi Jack, I have heard about this as well, you are not taught incorrectly. Let me try to explain it to you: if you pronounce ren with an r like the american r, then it is not entirely correct Standard Chinese. Instead, you have to stretch your mouth to both sides left right while producing the american r sound and shift the toungh slightly forward. Then, the r is changing a lot and sometimes it really sounds like what we in western countries would feel like zh. However, comparison of a sound in a foreign language to a sound in a language you are familiar with is never 100% match. Try to listen and observe carefully, eg. watching the Chinese news. Good luck, Valeria

ren not zhen

Hi, I would suggest you to make sure you find the good teacher. We have many dialects in China, some of which even can't be understood by people living in other places. Some Chinese people have problem speaking the authentic Mandrain.