I dunno, I've never heard the ZX1 so I can't say. However, I can say that the Sony PHA-1, Sony's other high end portable audio offering, is complete garbage. It also has high output impedance for whatever reason, making it terrible for audio devices with low impedance and all kinds of IEMs due to their typically uneven impedance curve. Additionally a good number of Sony's recent headphone output aren't particularly good (MA900 distorts when played loud, MDR-1A is pretty average, MDR-Z7 are clearly worse than most things in its price range) so forgive me if I don't think particularly highly of their portable audio offerings.
The whole rebranding of the Walkman into a series of high resolution playing audio players feels terribly cynical. There's an emerging market for it and it seems clear to me that their main focus is to find a way to push their DSD format. And the problem with this is that DSD is pretty much the definition of snake oil. Its a completely garbage format if you're one of those people who believe in the importance of ultrasonic frequencies. If you don't care about that, it doesn't do anything better than PCM.
To me, the device is no better than any other smartphone + good portable DAC/amplifier. Really, the Sony PHA-1 and DSD represent everything wrong that has happened with Sony - proprietary formats that don't really give the end user any real benefit and releasing products that are so bad that future attempts, no matter how good, are tainted.