[Opinions] Re: How do you pronounce ....
If you want the "official" pronunciations, you should probably ask on the Facts board. But I think it's GHIZ-layn -- at least, where I live I wouldn't be afraid to blurt that out. Could also be GHIS-layn. Anything else would be a foreign pronunciation (although another prn might be more 'correct').
Only an idiot would think you were an idiot for mispronouncing a name like this one.