Note that 25ms, while nothing compared with SLR shutter lag, can be noticeable when you are looking through the viewfinder
and moving the camera at the same time. The delay between the screen update the the physical movement
can be noticeable and annoying (causing some kind of motion sickness).
If you listen to yourself through headphones you can detect a delay of as little as 3ms.
Musicians have difficulty playing together with 10ms of latency.
I have't used the Z7, but I can detect this lag with every EVF I have tried (though they all have been more low-end than the Z7). It doesn't bother me though, but I am sure other people are more sensitive to this kind of stuff.
PS: I found a paper about VR that claims that even 15ms of latency can cause motion sickness:
https://arxiv.org/pdf/1801.07587.pdf.