Is it RAMADAN or RAMZAN? what is difference between RAMADAN or RAMZAN ?

Its Ramadan, but us asians have changed it into Ramzan! You can call either, but Ramadan is more appropriate as it is so in Arabic! its Ramadan, some people call it Ramathan, some call it Ramazan, but Ramadan is more proper.
In arabic its spelt and pronounced as رمضان so in english it should be spelt as Ramathan, or ramadan.
it is ramadan ramzan is just a different way people say it but the correct term is ramadan.
both...they're just english renditions of an arabic word....you'll see it spelled about five more different ways, too

neither, it's ramad'an or ramadhan, and most arab can say this letter that probably doesn't exist in any other language, arab who can't say it, say ramdth'an, also another special letter, i never heard an arab saying ramazan, maybe pakistani do 

its both.it depends on where you stay and your origin.some people use the word ramdan while others use ramzan.both are the same 

Ramadan in arabic pure, an ramazan in the egiptian, libanes and sirian accent 

Strictly speaking, it's neither. It should be transliterated as RamaDaan or Ramadhaan; where the D or dh is which is actually a tricky letter to pronounce and most current-day Arabs don't pronounce it properly (to know how it’s pronounced properly, listen to a professional Quran reciter, these guys are trained to pronounce sounds correctly). This phonetic sound actually exists ONLY in the Arabic language, that's why the language is also called "the language of the Dhad".

Accordingly, it is mispronounced by many non-Arabs, it is pronounced as z in Persian, Urdu, Hindi and many more so they sometimes transliterate it as Ramazan.

Also note that the first two a’s in RamaDaan are short vowels, the second (double a) is a long vowel. As a native Arabic speaker, I would prefer Ramadan because it’s much closer than Ramazan, which is actually a mispronunciation of a mispronunciation, plus, it implies that it’s a totally different word.