If your ISP has blocked OTA updates, use TFTP.
: Improves general processing speed and responsiveness of the user interface. Zte Software V0-1b07 -UPD-
Technically, yes, via the TFTP method. However, ZTE has implemented an anti-rollback mechanism in the -UPD- release. Downgrading will trigger a boot loop. It is not recommended. If your ISP has blocked OTA updates, use TFTP