I take the opportunity as I have the time, although I'm not an expert in translation, to make some work for Greek friends.
Unfortunately, I can't compile the files to xpz, although I followed the steps Swizzy described in
I attach all the necessary files, including the xpz I tried to export (but I see only english, no translation)
If anyone could help to that, I would appreciate it.
Thanks
EL-GR.xzp
language.dat
EL-GR.xml