Downgrade using Flashtool v0.9.16 to FW.534, Install DualRecovery from PC, Upgrade to Pre-Rooted .757 and follow the instruction which you will find on the thread by NUT. Done, now you are Rooted.
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My Evolution: Sony Xperia Z1 - UB + 4.3 Rooted + Deodexed, HTC HD2, HTC Diamond 2, HTC HD Blackstone, Nokia 7070 Prism, Qtek 9100, Nokia 3100, Motorola T720i, Nokia 3310, Sony Ericson PF 768 (Blue)
How Get Root on Sony Xperia Z1 with Locked Bootloader and the Latest Android 4.4