The Clan Zone is a feature in the Clan War introduced in the 17.0.0 update.
A clan zone can be captured by any of the 6 clans. The clan zone includes a task that all of the members of a clan could do. If the task is done, the zone is captured, and income can be collected from the occupied territories. Income includes Clan Silver and Clan Valor Points.
It is possible to capture an enemy zone, as long as there is a zone near the enemy zone. It can be done by redoing the task. Moreover, a clan and an enemy clan can do the same task to capture an uncaptured zone, and he first clan to complete the task will capture the zone.
The zones in the Clan War map usually are natural zones, like forests, hay lands, rivers and more, all shaped like hexagons. Sometimes, these zones can represent a map. For example, zone 1 represents Dead City and the task is to play one or more matches in Dead City in Raid.
Uncaptured zones are indicated by having no highlighted border on them. Captured zones are indicated by having a highlighted border on them.
In total, there are 271 Clan Zones that can be captured, so that means 271 total tasks that can be done in the entire map. However, there are 6 clans with their bases and each clan/base takes 3 zones which can't be captured, so 18 zones cannot be captured. Overall, there are 289 zones in the entire Clan War map.