What is the reason(s) for representing the French /J/ by /jh/ rather than leaving it as /zh/ which has been used by many Kurdish big names like Tewfiq Wehbi etc?

It is useful to understand the characteristic structure of different Kurdish dialects, such as Dimilí (Zazakí) Kurdish. At the current stage they use mostly North Kurdish Latin based alphabet, which is functioning quite well locally on dialectal bases, but when it comes to wider perspective many typographical misspelling might occur, like Cin = Women, Jin in north Kurdish and Jhin in Unified Kurdish. The concept will provide a better spelling system cross dialects and rule out typographic mistakes. This will make it easier for one to fully pronounce the combined letter /jh/  as one cluster as [ʒ], and one write the same word but pronounce it as a single single cluster [ʤ]. Please read more on this issue here.

What T Wahbi did was purely based his own home town dialect “Silémaní”, and his skill in English phonology and orthographic structure. The short experience of writing in Kurdish Unified has showed that /jh/ provide more accurate spelling than /zh/, please review Kurdish Unified texts at Kurdish section of KAL web site.