The confusion of 'd' and 'z'

[Human]

I've had this confusion for quite a while now where in India, bohris use 'z', sunnis use 'j' and overseas people use 'd' in certain words. Examples are:
Ramazan/Ramajan/Ramadan
Qarz-e-hasanah/Qard-e-hasanah

There are many other examples but I can only re-collect two for now. Basically I'm not sure which is the right one. Is it 'daal' or 'zaal'? Might be a very easy and basic question for the knowledgeable people on this forum and I might sound stupid, but just wanted to clear the confusion. Please give your input if you have an idea.

[porus]

The letter ض, Daad, is peculiar to Arabic and no sound for it exists in other languages. Arabs refer to their language as ‘lughat al-Daad’ , the language of Daad. South Asians use z as the nearest equivalent, which should really be used for ز , zayy. Elsewhere,the letter Daad is transliterated either as d or D in an attempt to make it sound more like Daad. I normally use D for Daad and d for daal.

So, for Bohras, RamDaan is pronounced Ramzaan, and QarD is pronounced Qarz

Other sounds that are confused by non-Arabs are ز, ظ, and ذ. I transliterate these as Z, z and dh respectively.

I do not always follow this convention on this board.

[Human]

^
Thanks Porus. Now I understand the difference.