To my understanding zone kills count only when you / the enemy is inside the capture zone. On certain maps I wish to have a second different circle around the first one, where kills would count as zone defense kills still, but not changing the actual area where you can capture.
As capture zones are sometimes only small buildings, this makes battle for a building quite unrealistic, any enemy 2m near the zone rushing to it surely does not want to play solitaire but attacks the zone. Also in reality you would attempt hold the building next to it, rule the street etc. (Btw. is it necessary for the enemy/me to be inside the capture zone to count as zone kill?)
For example if the enemy rushes through the capture zone killing half my squad, then exits to return through a different door and I go after him killing him 1.5 meter outside the zone perimeter, that should count as zone defense, even though we’re outside the zone and not capturing it. It might be so, but then the game does not “communicate” this fact too clearly for me.
To help that, zone defense kill marker skulls could be of a different colour.
One example where immediate surroundings should count as zone defense is the street around Fortified district’s “C” church (I guess that’s the map name). It’s completely legit to protect the zone sniping anyone from above. It’s hard to do so and stay alive if they are rushing from the buildings nearby, in which case I would surely consider it zone protection. (But a very limited surrounding only, 10 meters or so max.)
In the “B” bunker it would be the opposite: the current zone would be the kill zone where it’s worth dealing deaths, but capture zone could be reduced to the inside of the bunker. (Just an idea, it’s not bad as it is now so not necessary.)
Also I think in Vysokovo assault mode (?) the building in front of “E” building is an important location as it overlooks the field, so I would add it to the kill zone because of its strategic importance for protecting “E”, yet not add it to the capture zone itself.
One addition: it might worth considering to display the capture zone’s enemy/friendly count indicator in a smaller icon when in the kill zone, so you can rush inside in emergency. Don’t know whether that’s too much help for defenders though, and the small marker already displays when the zone is contested just it’s not detailed that much.
This could somewhat reduce the incentive to stay away from hot zones, by expanding it a bit.