It hasn’t been long since the Sony Xperia Z3 and Z3 Compact’s debut, but the devices have already received root and a custom recovery for those looking to tinker with them. The former exploit can be applied to any handset with the official launch firmware and will enable you to use root apps and hacks. The custom recovery, which allows you to install custom after market ROMs once they start rolling in, requires an unlocked bootloader (though we hear that’s easy enough to obtain right now).
It’s not that surprising that the Z3 and Z3 Compact have gotten exploited so easily. Developers have had plenty of time to play round the the Xperia Z2, and we imagine Sony hasn’t changed much to the base framework of those devices for this new set of hardware.
Sony is also famously supportive of the development scene and they don’t tend to put the shackles on as tight as other companies might. XDA has all the goods for you here (Z3) and here (Z3 Compact) if you’re interested, but always know that you proceed at your own discretion and are responsible for what happens to your own device.