well looks like you can be a friendly zombie. in vs on no mercy, the other team left their zoey person hanging off a edge they couldn't get back to. so as a Hunter I thought "ima pounce on her, knock her down". well I went to, couldn't. so I jumped uptop and started to swipe at her/his hands and it said help your ally" and it put that icon over zoey's head. so I held X and found out that zombies can revive incapacitated survivors and help them up. so I've been having fun with that ever since