Sony have now made the XZ1 and XZ1 Compact official. Both feature SnapDragon 835 SoC, 4 GB RAM, and 19 MP Sony sensors. This means that despite the size reduction, the XZ1 Compact still contains flagship performance.
https://www.notebookcheck.net/Sony-Xperia-XZ1-and-XZ1-Compact-now-official-and-both-get-the-SnapDragon-835-SoC.245992.0.html