Rollback Marshmallow to stock Lollipop(have checked firmware listed already)

Hi,

Please read complete
I have upgraded to Marshmallow and seeing downgrade in battery life. I want to rollback to Lollipop.

I have checked[List][FTF] Stock Firmwares + Concept (24/06/2016)
using : D5833(India)
I have check the FTF file for India and it says customized whereas i want to rollback to Sony Z3 compact stock Lollipop 5.2 or 5.1(whichever was the last update for this model) original stock version not tempered with in any way. Can you please guide me if there is a way to get that.

Thankyou for reading my post

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