Asus ZenFone 5Z (ZS621KL) Stock ROM (Flash File). Free download Official Firmware ROM for ZS621KL. You can use it to update and downgrade the device, fixing the device facing bootloop issue or any software issue.
– Make sure that Device battery is charged more than 30%.
– Extract the firmware file with the latest version of winrar or 7zip.
– Always check Device model before downloading the firmware file.
– Also install a latest version of USB Driver before installing firmware file.