By now you've probably noticed that even with social > quick join turned on you can't see the lvl60's game with the lowbie, but here's what you can do. Fastest way to complete the run imo. Talking maybe 4-10s max, no delay only your own latency.
lvl60 and lowbie join game kill ZK
lvl60 leaves and resumes
lowbie opens social menu in game (o default)
right clicks lvl60s name
click join game
60 leaves and resumes
repeat ad nauseum
No having to invite on one screen and accept on another. So long as quick join is turned on on the 60's options and both are friends. Should shave a couple seconds off current runs/scripts.
Only way this could slow down your script is if you had people on your friends list that would change the position of the lvl60.