This is where ur relationship with a native English speaker comes real handy I reckon..and it took her a whole damn week to convince me that I was not pronouncing it right and one more week to get it fixed..she took a complete different approach but let me give it some Nepali touch... Let just assume here there is only one alphabet among those 2 and it's "g". You know how to pronounce it right??? Okey now pronounce "g"as hari bahadur would do it, and again try to pronounce the same 'g' as Rajesh hamal would have done it. The first one was your G and the latter was one your Z.

It's just my opinion though :)