Your timeline needs some love as well, I'll help you with the best I can and maybe I can clear some things up for you.
I think your start is pretty accurate based on Z's 911 call and the girls account.
At the:
1:38 into Z's call we hear the "these assholes always..." line, this is when M starts walking fast with Z following in vehicle
2:08 "shit he's running" (verified by GF account told him to run)
2:14 'ding ding' of interior bells/door slams shut (Z on foot now)
...So at 2:14 Z is on foot as evidence by running and heavy breathing.
2:23 "are you following him?"
2:25 "yep"
2:26 "ok... we don't need you to do that"
2:28 "ok" (Z agrees but does he stop?)
2:44 heavy breathing stops... you can hear first knocking on window/door (someone's house he know's? Not sure) So he is still outside on foot, 16 seconds after saying OK.
2:47 you can hear him knocking even louder now 'knock, knock, knock'
3:08 knocking very loud now So still outside on foot, 40 seconds after saying OK... still talking to dispatcher on phone giving directions to where he parked the truck...
3:30 what's your appt number?
3:33 it's a home it's 1950... (more knocking)
3:36 "oh crap I don't want to give it all out I don't know where this kid is..."
So still outside on foot searching for Martin, not wanting Martin to potentially overhear where Z lives, 1:08 seconds after saying OK.
3:42 dispatcher asks do you want to just meet with them at the mailboxes then...
3:44 "yeah that's fine"
3:48 "actually, could you have them call me and I'll tell them where I'm at?"
3:55 "do you know my number?"
4:02 dispatcher says I'll let them know to call you when they're in the area
4:05 "thanks"
So that's 1:37 seconds after he said OK he was still on foot. That's almost 2 minutes after he exited the truck and started running. Phone call ends and it doesn't sound like he is looking for any street signs or looking for his truck, or the parked truck meeting place would have been fine and he wouldn't be changing his mind and telling them to call him so he can give them his new location. He for sure wasn't in his truck...
We know that 1 minute goes by after Z's call ends and the fight and shot is fired and M is dead 70 yards away from his back door between rows of buildings some distance from Z's truck still.
Still have no idea other than Z's testimony who hit who first, but it all went down and was over pretty quick after the call ended.
EDIT: oh the audio link that matches the time stamps...
http://www.youtube.com/watch?v=o9A-gp8mrdw