They say it's pronounced "Zigh". I am a non-native English speaker, so I am not even going to try to question this.
Anyway each hint is helpful. I'll google for that.
For completeness, the vowel is the dipthong 'aɪ', pronounced like the 'i' in the word 'price', discussed on the same wiki page.
In Chinese the "x" would be pronounced like that: https://en.wikipedia.org/wiki/Voiceless_alveolo-palatal_fric...
So not really a "sh-" either, but English doesn't have that sound at all I believe.