Trying to update my Z3 (d6616) to 6.0.1

I've been trying all day to get this to work. I've tried different firm builds and three different versions of Flashtool. I did this no problems with my old Z1.

I keep getting the same error no matter which firmware I use:
11/009/2016 01:09:35 - ERROR - root : this bundle is not valid

Currently using
No root, stock phone running 5.0.2

Flashtool Version 0.9.19.8

I have tried all of these firmwares...

D6603_23.5.A.0.575_1288-7827_R4D.ftf

D5803_23.5.A.0.575_1289-7524_R5D.ftf

D6646_23.5.A.0.575_1299-7736_R2D.ftf

I've also tried creating my own .ftf but same thing.

Any ideas?