download heimdall and put your phone in download mode. you can extract to contents of the LP rom with winrar or 7zip. in heimdall you can then select which parts of the rom you want to flash. if you just flash boot.img, system.ext4, data (maybe cache to, you'll probably have to wipe that and data anyway after flashing). and recovery.img the phone will probably boot but wifi and modem might not be working, I dont know. experiment with flashing the modem firmware and NON-HLOS for wifi, if they dont work you are probably better of waiting. look up guides on xda on how to use heimdall and what all the different files are. you probably shouldn't flash any files that are related to the bootloader.
the 4 files i mentioned first are what you would find in normal rom like cm (except for recovery in most cases) so flashing those won't brick your phone. I can't say for certain for any of the other files.
for those first 4(3 without recovery) files you can also flash them by making flashable CMW zip (you can look up xda guides on how to make them).
EDIT: just flash a stock rom if you want to get your phone back to kitkat even if your flashing a custom rom. any custom roms don't contain any modem and wifi firmware. also since the latin modem is probably different from the European version. firmware will probably not work since it's different hardware.
I would be glad to help but I will not be able to poke around the phone until the weekend... If anybody is whiling to help that would be great, but before that I have one last questioning to make.
Would some Dev around be interested in taking a deeper look on the real differences of those two ROMs variants? If someone with deeper expertize could check the coding differences between them we surely would reduce the risks of just randomly flashing stuff on our phone, hoping for some magic dust hit them on time. I ask that because even with KK Roms the error is the same.... So we could take a deeper look in two similar KK roms...
Are those ROMs and devices really that different, besides the extra "L" and probably modems?
Getting to know the real differences would save us usually months of waiting for an stock update or months with crippled devices due to trial and error patches, once European ROMs are more often updated than Latin ones.