Since 8.0 <artifact relative name> supports archived files, so "!/" delimiter can be used.
If you download the artifacts from within a TeamCity build, consider using
teamcity.auth.password system properties as credentials for the download artifacts request: this way TeamCity will have a way to record that one build used artifacts of another and will display that on build's Dependencies tab.
"USER" and "PASSWORD" - credentials of a valid TeamCity user (that you can login with)
"teamcity:8111" - TeamCity server URL
"USERNAME" - username of the user to make the system administrator
"XXX-YYY-...-ZZZ" - the authentication token retrieved earlier