Since zones are instanced by level, you can't tell what clans are active in a zone. Below the Clan Control info there should be a message that shows the number of members in the zone for each clan. It would help gauge what the competition is like for control over each zone other than only the current kill target. This count would span all instances.
Ex: "Clan members in this zone: RaZR (2), BEST (1), ELXR (3)"