Try this:
local_machine_time = emailtm.Format("%a, %d %b %Y %H:%M:%S") + " (" + (0==_get_tzname(&ret_value,get_tzn,sizeof(get_tzn),0)?get_tzn:"") + ")";
Good luck.
[edit]
list operators (,) work like stack from left to right. the last parameter (thats the right) is used.
_get_tzname(...),get_tzn
should work too. but only if
_get_tzname
dont fail.
Regards.