I've heard some people pronunce it zhen and some pronunced it ren (spoken like "you had a hot potato in your mouth") and because of this I am very confused what is the correct pronunciation.
The place of articulation varies connsiderably from the approximant /ɹ/ sound of the English phonem usually transcribed as /r/. Eng. RP (received pronunciation) is a true retroflex /r/ (like Slavonic pron.) and is also a distinct from what I would here as the initial in 人, or 日 for example. I've lived in several areas and have been exposed to a number of Mandarin and other Chinese dialects. With Chinese pron. I tend to think of what is the most widely understood, rather than correct or incorrect.
"Similar to s in pleasure in English, but with a retroflex articulation. Otherwise, some speakers pronounce it as an English R, but lips are unrounded."
Denti-alveolar and retroflex series
"The retroflex consonants (like those of Polish) are actually apical rather than subapical, and so are considered by some authors not to be truly retroflex; they may be more accurately called post-alveolar. Some speakers not from Beijing may lack the retroflexes in their native dialects, and may thus replace them with dentals.:26"
This is true in my experience.