GetZoneIndex is bugged
 

According to the api, GetZoneIndex is supposed to work like this:
GetZoneIndex(number zoneId)
Returns: number zoneIndex

I was playing around with it today, and I find that GetZoneIndex returns "1" for

Gold Coast (zoneid 518)
Hew's Bane (zoneid 512)
Craglorn (zoneid 352)
Khenarthi's Roost (zoneid 293)

and others

Where should I report this?

edit: tested without any addons enabled

Those are not the correct IDs for those zones--these are the correct zoneIds for the zones you listed:

823, The Gold Coast
816, Hew's Bane
888, Craglorn
537, Khenarthi's Roost