I found zenphoto is mixing gettexts domains during run script, when theme has its own lc_messagess/domain. If there is no solution for this, this can be the solution (usable also for plugins etc):
New custom function for getting string from another than standard (zenphoto) domain. Something like
`
gettextd($string, $domain) {
1) set $domain as domain
2) get string
3) set back default/previous domain
}
`
_() function is nice helper. :-)