I just flashed xiaomi.eu_multi_ido_V7.3.1.0.LHPCNDD_v7-5.1.zip to my Redmi 3 Pro and went into a lot of issues...
First the phone didn't boot anymore, just vibration and short flashing of Mi logo - that twice.
When trying to enter TWRP... nothing.
Fastboot was possible at second try and download also worked, well it worked entering.
But flashing any ROM was impossible as the bootloader was locked - I had to unlock it with MiUnlock (I just tried after around 2 hours of experimenting). So the unlocked bootloader was locked during flashing of the ROM!