IMO Chris Serino felt GZ chased TM with his car down TTL, causing TM to run. That's what he's likely hinting at in the final interview IMO. GZ doesn't take the suggestion to amend his statements. Why did they offer him the opportunity and why did he refuse? Shortly before this final interview GZ told SPD that TM approached his car in a doubling back/circling move from the cut thru area, and recalls the specific detail of telling dispatch that TM had his hand in his waistband.
With the context of the non emergency call, I can't really imagine at any point he chased him with his car in any sort of reckless manner. There's no engine roar, wind noise, etc. Plus, if GZ was visibly speeding towards Martin, would he have have likely returned to the vehicle? He probably would have just kept running.
I tend to take the NE call for what it is, GZ had no idea what was going to happen and had no reason to lie at that point. He's no criminal mastermind who is trying to craft an alibi after he just spotted the kid minutes beforehand.
Zimmerman at times seems pretty scattered brained in his recollections, but honestly in that sense he is basically like every other person I've known with ADD. To me, his events leading to exiting the truck seem to line up given that he probably dialed the number to dispatch while at or possibly departing the clubhouse and connected while driving down or parking his truck on TTL.
The part of the NE call that always stuck out to me is when he purportedly asked the dispatcher "How long until you get an officer over here?". His tone is obviously distressed and uncomfortable. Regardless if GZ followed him slowly or quickly in his car, TM was clearly unfazed and became close enough to clearly unnerve GZ.