Dude no i never said Allah is Rab of Muslims alone but parsi used word Khuda for their GOD..
unless their God have same attributes as God of muslims then it dont matter whether you use khuda for allah or vice versa.
Again there are many words parwardigaar, data, malik, rab etc that peoples use for Allah. Allah has 99 names so it dont really bother me much but i personally prefer to use Allah
We all will agree that definition of God vary religion to religion. hindu bagwan is different than muslim ALLAH . So can we call Allah as bagwaan? Christian Consider jesus as God/son of God so can they call their God as Allah?
also non persian/urdu muslims dont even know what is Khuda.. when you will say Khuda hafiz to them it will not make any sense to them..
Al-zakir@ hafiz is from arabic hifz mean protection