www-misc/zoneminder-1.27.0 app-arch/zip should be added to the deps, otherwise the "Export event as ZIP" -function in the zoneminder-webui fails with an unspecified error. The "vlc"-use flag should require the vlc-ebuild to have the "live"-use flag. If vlc is built without the "live"-use flag, it lacks the rtsp-client-support, which is propably the main reason the use vlc with zoneminder.
Fixed in 1.28.0.