Recently Sony was launched their smartphone Xperia Z4 in Japan and after that some new devices of Sony listed in a data base. Probably the new devices are Xperia Z4 Compact and Xperia Z4 Ultra.
The certified model numbers – E6833, E6683, E5803, E5663, E5563, E5333 – spotted listed in Indonesian Postel database. And two of them expectedly has Xperia Z4 Compact, Xperia Z4 Ultra, Xperia C4, and more.
If you look towards the previous trend the Sony used “D” for the Xperia Z3 Line and for the new Xperia Z4 line the company use the alphabet “E” for the initial code name. besides these code name there is no information available over the internet about the smartphones. The E5803 is probably to be the successor of it which may be called the Xperia Z4 Compact. Similarly, the E6833 is expected to be Xperia Z4 Ultra.
The smartphones are seemed to be identical, but the name of the devices are different and might become with the hardware difference too. Well, we can not say anything before the time we need to wait till official confirmation.