Ok So I had a smearing problem which is what I was reading about troubleshooting when I read this is the preferred method for RTSP streams in ZoneMinder. I *think* that if your RTSP stream works via FFMpeg then it should work this way.
A reason this is preferred is it forces TCP connections. There may be more, but it worked right away for me, no smore smearing and I didn't change any settings in my Camera.
Basically you are going to select the following
Source = Remote
Remote Protocol = RTSP
Remote Method = RTP/RTSP
Annoyingly [I really hate when they make you take apart a working link because every site does it different, do I put in the http:// or do I leave it out, do I add the "/" or do I leave it out, but anyway]
You need to convert this example full RTSP stream link into 3 parts. Example: