I never compared the 1A and 1Z. The step up on the ZX2 I previously had was enough for me to stump up for the gold brick. Note that the 1Z throws away the wireless capabilities in pursuit of ultimate SQ, so if you want a one stop shop for streaming services and local storage then I’d look elsewhere. With 256Gb on board and a 400Gb Micro SD card, I’ve got ~600Gb of storage so I can fit the majority of my music collection (in ALAC) onto it. When I use it at home, I also use it in USB mode, fed from a Project Streambox S2 and this provides my whole library and Tidal via Roon.
10 months on, I think I can say that the 1Z has probably been one of my best Hi-Fi purchases. Used at work with SE846 IEMs or at home with Sony Z1R ‘phones it just sounds sublime and I could happily live with it as my only music system if I ever needed to.