Please note that at this point of writing (June 6, 2019): THETA+ app does not recognize ‘Theta Z1 Stitcher for evaluation (Unreleased) converted file’ as Equirectangular panorama, therefore you would need other app to process it further
iOS/iPadOS (at this point of writing — June 6, 2019, I don’t think we can…):
Theta Z1 Stitcher developer also created MiSphere Converter app. This is for other 360 camera to convert Dual-Fisheye to Equirectangular. However, this app does not recognize THETA format of (Lightroom’s) jpeg.
I don’t think you can transfer RAW (DNG) file directly to iPhone from THETA Z1. You can save RAW file using USB Data Transfer Plugin, however, iPhone does not recognize the file, therefore you cannot copy it to iPhone. The easiest way is probably to copy the file to Macbook and air drop it to iPhone.