I just received this today and my initial impression of the case was that it was massive ! I keep my Note 3 in a book case when I compared it, I thought their roughly the same size anyway but the ZL will offer much better protection and its batter life will be legendary so I just went for it. The battery came with a 58% charge in it. I didn't charge it for 12 hours as with that level of charge still in it, it sounds fairly excessive so I tried to drain the battery and it was going OK although as I made changes to my ROM to allow for better battery life, it became harder to drain it.
I resorted to using a fast discharge app which is designed to drain the battery. It was going well and I placed the phone screen side down on my laptop cooler in order to prevent possible over heating. When the app indicated the battery was at 1% i stopped everything and uninstalled the app and then continued to just scroll through screens hoping it would just turn off any second now. It took 2 hours of playing HD video with the torch on to reinstalling the app to drain the battery from 1% to dead.
As annoying as it was, I'm kind of happy its capable of that kind of power and as it has begun its 12 hour charge, I hope to get days out of this as I don't regard myself as a heavy user.