As an owner of both (still own my ZT as well as a 500M) I would pretty much agree. there are some things the EF does better though, but in the end, the video processing and motion on the ZT is better with all sources. Though with the newest firmware most motion issues with the EF have been resolved. The ZT also has slightly better shadow detail, since the EF has near black issues and the ZT is at 0.006 MLL it has better shadow detail, which is strange when you think about it because the EF is pure black, but something about that 2% level it is never 100% precise. It either looks like it might crush it, or it is slightly elevated, mainly in bad sources though blu rays are not that much a problem. Not saying the EF looks bad on sources like cable, but it's more unforgiving with flaws and low bit rate, bandwidth, poorly compressed, or mastered content.
We've yet to see what the 2016 models will bring, and honestly for movies I would say that if you wanted to upgrade now is probably the time to consider, especially if you want 4K, HDR, etc, etc. If you own a 2013 Panasonic, or F8500, or 500M OLED is the natural path to follow.
One thing I find interesting is that having the 3 panels I got and checking content between the 3, having something that displays true pure black is eye opening. I don't look at the ZT or 500M in the same light anymore.
Plus in 7 more days the 4K blu ray player releases, hopefully the movies I ordered will be in also or at least a few. I cannot wait. Going to be quite the experience between 4K, HDR, and Atmos...I'm going to be watching a movie every night lol
Oh and to add, passive 3D on a 4K display is ridiculously good. I'm not a huge fan of 3D, but the difference is pretty impressive.
If you don't need to upgrade or don't plan on keeping the ZT also I would wait, maybe 1 more year but they are damn close, and I mean damn close. Depending on your watching habits and environment the OLED even now might be a better option though in all honesty.