I'm currently trying to improve the french translation, and I'm starting to understand why some strings are not correctly translatable. Zabbix front-end sentences are sometimes defined as "a (translatable) string and a space and another (translatable) string" etc.
For example :

S_IN.SPACE.S_MAINTENANCE => "In maintenance" in english, "En maintenance" in french => ok
S_IN.SPACE.S_GROUP => "In group" in english, "Dans le groupe" in french => impossible to translate
S_IN.SPACE.S_GROUPS => "In groups" in english, "Dans les groupes" in french => impossible to translate
S_HOSTS.SPACE.S_IN => "Hosts in" in english, "Contient les hôtes" in french => impossible to translate

The web frontend translation should be based on groupes of words and not single words. For example, replacing "S_IN.SPACE.S_MAINTENANCE" with a new "S_IN_MAINTENANCE" or "S_HOSTS.SPACE.S_IN" with "S_HOSTS_IN".