problem with installing cutom recovery in xperia z1

hello
i have a problem
i want to install custom recovery (twrp) in sony xperia z1 but i can,t do that
please help me
notes :
my phone model : c6902
my phone is rooted with kingroot app
my phone build number : 14.6.A.0.368
my phone android version : 5.1.1
i unlocked the bootloader of the phone with sony service
my phone is up to date with sony updates
i don,t want to downgrade the phone to kitkat

i am wait for your answer and it is my first try with xda forum
please help me

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