I have my ZS100 in manual mode so I can adjust the aperture and shutterspeed on the fly. I also have my focus on manual so I can use the lens ring when necessary.
I tend to shoot in 4K 30p, but the only major pitfall is that you lose optical stabilization shooting in 4k on the ZS100
I set the aperture at f5.9 since that's the lowest aperture you can get zoomed all the way in. It prevents having the video get brighter as you zoom out
I have the shutterspeed at around 50 or 60 because that's the optimal range when shooting 30p. I micro-adjust as low as 30 if things get darker at a show or crank it to 80 or higher if an intense spotlight comes on (but only after I've closed the aperture to the max f8)
How I focus is by customizing one of the buttons on the back of the camera to do an auto focus and periodically autofocus again as the subject moves around the stage. If the autofocus screws up, the focus ring is there in an emergency.
The last few pages of videos from Coachella 2017 and U2 I have on my YouTube channel are all shot with my ZS100:
http://www.youtube.com/magmazing