Add the following to your shops.
In \Zoneserver\ZoneData\Shop Make 2 text files (if they dont exist) called 1032 and 1033.
Add this to those text files and save.
9814 9933 9934
The above three codes are the ones for Gold Small (1Bill) , Gold Med (2 Bill) and Gold Large (4 Bill).
Now go to the storage and try converting WZ to Gold and Gold to WZ. Should work. WZ to Gold was already working in these files. It was just a matter of adding the Gold to the shops to make Gold to WZ work out too.
Credits: Ins@ne (ragezone.com)