I have recently rooted my Xperia z ultra. and now i want to install custom ROM in it. I have searched internet. but i am not able to find any safe way to install custom rom. how can i do that?
Follow these steps for installing custom rom :
1.Unlock bootloader from sony official website instructions.
3.Download custom rom like LineageOS or Resurrection remix whichever you feel good.
4.Boot to your recovery , wipe System data and install custom rom with Gapps.
5.Reboot and enjoy.
Follow these steps for flashing.
1) Download a ROM of your choice.
2) Connect your device to your PC using the USB cable.
3) Copy the Custom ROM.zip file from your Desktop over to the root of your SD card.
4) Turn OFF your device, and turn it back on by holding Volume Up and Power buttons together.
5) Your device should reboot into recovery mode(In the recovery mode, the Volume buttons are used for navigation and the Power button to make a selection)
6) Select Backup and Restore -> Backup.
7) Once done, head back to the main menu.
8) Select Wipe data/factory reset.
9) After this, head back to the main menu by selecting Back.
10) Select install zip from SD Card followed by choose zip from SD Card.
11) Choose the Custom ROM.zip file you copied earlier to be flashed on your device.
12) When the ROM has been flashed, reboot your device by selecting reboot system now, and you will be done.
You can research more over here.