If it's just the Z systems, then the relative impact of 1.9 does not explain the CPU load. None of the Z systems consumes any noticeable CPU resources with 1.9. So the CPU load is generated elsewhere. Can you test it on a normal Windows PC or have you only Linux?
Only have Linux at the moment I'm afraid.
Another test that you could do: close all sessions and remove the EA from the chart, then replace Libraries\ZorroMT4.ex4 with the previous ZorroMT4.ex4 from version 1.8. This is the only file that uses a little more CPU resources than before due to a faster reaction on commands. Leave the other files unchanged. The EA will then report bridge version 1.8, but it's in fact 1.9. Please let me know if this has an effect on that 100% CPU load.
I tried this on Z7 and no, it has the same effect as entirely 1.9. 100% CPU usage.
Here's a pair of screenshots of my server load with a 1.9 instance (top) and without (bottom):
https://imgur.com/a/0NZOi
