if the zone vaues represent object identification certainty then there are other aspects of an object that might affect this value other than location within a zone, object that are moving are much easier to objects that are perfectly still.
additionally object is mch harder to identify when they are camouflaged against their environment, because of either having simillar colors or patterns to the background.
additional factors can be incorporated the visions model by giving an object a bonus or penalty based the attribute an object is moving might add to its object identification certainty.
if an object in the peripheral vision would normally have an object identification certainty then a camouflaged object in that same spot would essentially be invisible,
note that the examle zone value number and bonus penalty vaues used for illustration purposes and finding appropriate number would depend on the particular games and would require tuning and testing.