If you've been following Google's Android 5.1 rollout, it's no secret that the release to GPE devices is well underway. So far we've seen the stock Android variants of the Moto G, LG G Pad 8.3, and HTC One M8 get the update, and now it's time for Sony's massive Z Ultra GPE to have its turn in the sun.
The build is LMY47D and it's not entirely clear yet how big the OTA is. We don't have a link to the actual ZIP file yet, but once we do, we'll post it here. Presumably, the OTA is rolling out in stages so if it's not available for you yet, hang tight. It should be soon.