The problem can best be seen, just as I detected it, playing first and third person games that use the two-thumb control scheme.
It turns out that when we slide a finger on the screen, the response is 1.5x slower than with 3 fingers, with three or four fingers it's smooth. When we slide two fingers on the screen, not only does the sensitivity decrease, but the latency increases by 2x each. Causing an effect like using a low DPI mouse playing with a sniper on a shooter.
There's an application on the Play Store called "MultiTouch Tester".
With the application open:
Slide one finger on the screen (preferably slowly for a better view of the effect) and notice it's not that smooth.
Now hold one finger anywhere on the screen, and with another finger, slide slowly as you watch the graphic response to your command stutter.
With three you should slide it medium speed to see it failing.
It happens within system, games ... everywhere. Seems like bugs that other brands had but they fixed with an update (e.g. Poco, Huawei ... even Samsung).
Here are some videos that demonstrate the situation:
[In order to access the linked pages, please, erase the "space" between "." and "com"!]
In the first video, a comparison that demonstrates the ZenFone 5's ironic victory over 5Z:
In the second, a full screen view of how problematic camera control and aiming accuracy become in games:
The third, in fact, is a YouTube channel, where videos are posted that demonstrate the same effect to two-touch controls:
Searching YouTube and ZenTalk isn't hard to find more users having the same problem either. From the reports, it is present in all 5Z, in any version, ever since.
1) Is it a hardware quality or a firmware problem?
2) What could be causing this?
3) Is there a software solution?