I stumbled upon ZTE app's at APKMIRROR by accident. These are in APK format and can be downloaded for free.
Among them is the APK of the ZTE Stock Music Player in a more recent version than ours.
When I install the APK the error message "The package conflicts with a file with the same name"
I have also downloaded a more up-to-date Gallery apk and I could easily install it as an update of the existing one.
Can someone give me a hint why that could be?
I am not gerooted.