As you can see 4.23V is way lower voltage than 4.45V in ZF8 (40% operating voltage span increase!!!). I also had one Lenovo phone, which battery lasted 5 years and is still ok. Max battery voltage was also 4.2V. But all later phones charged to 4.3V or more and all degrade noticeably after year or two.
Thanks for your post, it makes sense why 5z lasted. I will definitely continue charging it only to 80% (4,3V). 50-70% is enough for one day for me.
Sorry for off topic, maybe moderator can move this posts in different topic.