The Z1 has both JPG and DNG images. The DNG images are not stitched. You can convert the DNG image into dual-fisheye image in any format you want, such as JPG or TIFF with the free software DarkTable.
see the workflow here. Just ignore the stitching parts.
Please post more information on your workflow and if you’re looking for this type of one-type dual-fisheye with manual conversion or if you’re looking for batch processing.