Converting .zip files directly to .obb format.
Converting Zipped Files directly to Android Opaque Binary Blob Files (.zip to .obb conversion) doesn't appear to be possible.
Should, however, the .zip file's content be related to an actual Android app (.apk file), typically, that means there will also be an .obb file in your .zip archive. In that case, extract the .zip file first. Move it then to the default .obb folder on your SD card.
The database currently does not contain any zip software converter.