What am I doing wrong? topic

Okay, So heres the problems im having, I have unlocked the bootloader and flashed the latest version of TWRP and have flashed the lollipop stock rom but thats as far as iv got, I try and flash a custom rom that uses say Aroma installer and all that happing is it get stuck on formatting partitions and will sit there for ages and then it says unable to unable to mount '/system' and i have to reformat the storage and flash the stock rom. What am i missing here. this is the info that i think you guys need about my phone. This happens when flashing all different types so please dont tell me to ask the maker of the rom as iv tried loads all the same error.

Code:

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c:\mini-sdk>fastboot getvar all
(bootloader) version: 0.5
(bootloader) version-bootloader: 1.57.0000
(bootloader) version-baseband: 4T.28.3218.04
(bootloader) version-cpld: None
(bootloader) version-microp: None
(bootloader) version-main: 6.12.161.8
(bootloader) version-misc: PVT SHIP S-OFF
(bootloader) serialno: FA34FW906950
(bootloader) imei: 354436050888336
(bootloader) meid: 00000000000000
(bootloader) product: m7_ul
(bootloader) platform: HBOOT-8064
(bootloader) modelid: PN0710000
(bootloader) cidnum: VODAP001
(bootloader) battery-status: good
(bootloader) battery-voltage: 4015mV
(bootloader) partition-layout: Generic
(bootloader) security: off
(bootloader) build-mode: SHIP
(bootloader) boot-mode: FASTBOOT
(bootloader) commitno-bootloader: dirty-6d8a0b9b
(bootloader) hbootpreupdate: 11
(bootloader) gencheckpt: 0
all: Done!
finished. total time: 0.073s

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Hope you can please help me