I've not had any luck finding a thread on this as it brings together a few keywords that result in many hits, so apologies if this has already been covered.
I was thinking about the reasons Z would use a .22 at LHR when he used a 9mm for subsequent attacks. Whilst a .22 is capable of killing it is undeniable that it is less likely to result in a fatal wound (unless a headshot is achieved). It seems like an extra chance to take - why not use a gun that is more likely to kill with less shots? Noise volume of the shots could be one factor, but I deem that fairly unlikely due to the remote location, unless he was particularly nervous if it was his first time.
The most likely reasons I can think of are accuracy and the length of the barrel on the suspected brand of pistol used, which allowed Z to add his customized torch.
This is interesting as it implies he was prepared for exactly the situation that occurred - Betty Lou running off and presenting a dark, moving target- so may offer some insight into his preparation of how things went down. Interesting that he did not prepare a torch for BRS, he may have decided not to allow that to happen a second time and fired repeatedly into the car to prevent them exiting at all. Much better to do that kind of shooting through car windows/upholstery etc with a 9mm than a .22 from what I have read online. I've fired .22 rifles and held the rounds in my hand, I certainly wouldn't be confident they would pass through nearly as successfully as a 9mm but I've never fired something of that size so don't know for sure.
I find a .22 rifle an odd choice for Domingos/Edwards as well, again not sure why a low caliber would be the choice weapon.

