why should I believe him at all?
I should have covered this in the previous post.
You don't have to, but you are going further that "I don't believe him" You are going to "I don't believe him, therefore the opposite of what he say must be true" and "I don't believe him, so I am allowed to fill in the vacuum that exists without his claims with my own made up narrative."
Even without GZ's story there are enough things in evidence to note your narrative is wrong, and in many place there simply is not any evidence to claim to know anything at all.
GZ told the NEN he had lost sight of TM, that he didn't know where he was. There is zero evidence that he was lying at that point. He also told the NEN Operator "Okay" when told he wasn't required to follow, and there is zero evidence that he continued to do so, or look for TM after that point. Any claim otherwise is total and complete speculation. Even according to RJ's testimony TM had lost GZ.
The witnesses who testified to hearing the confrontation place it at the T with the subsequent fight moving down the dog path. RJ claims that TM saw GZ behind him again and turned around and spoke first. We don't need to take GZs word for that.
GZ was the only one with injuries sustained by being beaten in any form. We don't need GZ's word for that, and yet RJ tells us that immediately after the confrontation she heard a blow being stuck. If TM was free of any damage from being hit, who delivered it and who received it?
TM was on top of GZ, his arms moving in a motion that defined an attack of some form according to a witness to the actual fight. We don't need GZ's word on that.
According to the testimony od the experts, the gun was fired touching TM's clothing, but 4-5 inches from his body. What position was TM in for his clothing to be 4-5 inches from his body? We don't need GZ's word for that.
So according to the witnesses, TM lost GZ. TM was running away, heading home according to RJ. 4 minutes later TM was back near the T and according to RJ confronted GZ by questioning him first. That this occurred at the T is backed up by other witnesses. From injuries on both parties, only GZ received punches, yet RJ claims to have heard the blow land after GZ demanded to know what TM was doing there. According to a witness, TM was on top of GZ attacking him while GZ screamed for help. According to the gun experts, the shot was fired when TM was in a position that resulted in his clothing being 4-5 inches from his body.
All of that and no need to take GZ's word on anything.