How to allow apps to delete SD card content
Since 4.4 the "WRITE_EXTERNAL_STORAGE" permission no longer grants WRITE access to the secondary(external) sdcard. (This is a simplified explanation, 4.4 did not force this change.)

The necessary permission to do so ("WRITE_MEDIA_STORAGE") is only avialable to system apps.

Since 5.0 it is possible to gain write access through Androids storage provider system, this must be implemented by the developer though.


The native file manager app should be able to write to the external sdcard, check if it requests the "WRITE_MEDIA_STORAGE" permission.
SD Maid will support deletion &amp; renaming with the next update (3.1.2.0+) through the systems storage provider.
I don't know about SandDisk Memory Zone.