ZOC is typically used in games to represent a zone of control over locations adjacent to combat units, not (from) buildings/towns unless there's a combat unit in that town (in which case it's the unit, not the town, which exerts zoc). The OP is refering to zone of influence that is part of town' growth, totally unrelated to combat units or heroes.
ZOC could've been used very effectively on the tactical level to define front/side/rear facings for combat squads & heroes. A hexagon tactical map is always a better choice at the tactical scale than squares for this reason. The tactical combat system, as of now, is too simplistic to deal with combat facings, hopefully this will be added in the future to further enrich the game.
... there's a whole lot that can be done with combat systems that utiliize zoc. For fantasy type man-to-man combat like we have in this game, we can:
1) define f/s/r facings like I mentioned above
2) additional mp costs should be associated to move from locations zoc-to-zoc
3) shield bonuses or negations can be easily determined from zoc orientation
4) realistic modifiers based on side/rear attacks can be added to the system (which should also affect the defender's morale).
.... those are probably the main reasons games use ZOC, although effects vary with game scale (tactical squald level vs brigade level vs divisional level for example).
