The following snippet in zshrc causes iso-term to fail:

xsource "/etc/default/locale"
for var in LANG LC_ALL LC_MESSAGES ; do
    [[ -n ${(P)var} ]] && export $var
done

iso-term tries to replace UTF-8 in the environment with iso885915 (useful if 
you have to edit iso88591 encoded documents in the shell) but as the global 
zshrc sources /etc/default/locale and exports environment variables again this 
doesn't have any effect.

Frank, do you have any ideas for an elegant solution? :)

regards,
-mika-