After poking around with other file managers, it seems Sandisk MemoryZone copies files from internal storage to /storage/extSdCard/DCIM/Camera/xxx . This makes the standard Gallery app unable to find them (e.g. it still thinks it is at /storage/emulated/0/DCIM/Camera/xxxx ).
BTW I noticed that normal jpg/mp4 files stored on the external SD card from camera/video app are in /storage/extSdCard/DCIM/Camera/xxx .
All I can do from the MemoryZone app is copy the file back to internal storage, and then delete from internal storage. No option to move it back (or delete it), so I am still left with the file on the external SD card as well as a new copy of the photo on internal storage at /sdcard/MemoryZone/Android/data/com.sandisk.mz/files/DCIM/Camera/xxx .
