Before flashing, read out the existing firmware using a tool like dd or the manufacturer’s readback utility. Save it as backup_old.bin.
If you're unable to find the firmware on the manufacturer's site, you might consider: zl782mbv20 firmware download free
I cannot recommend a specific free download link for “zl782mbv20 firmware” because there’s no single official source. Searching blindly will likely lead to malware or bricked hardware. Your safest path is to identify the full device model and seek firmware from community forums where others have tested and shared it safely. Before flashing, read out the existing firmware using
If the device is from AliExpress, Banggood, or a white-label brand: Once you're on the manufacturer's support page, search
Once you're on the manufacturer's support page, search for your device model ("zl782mbv20"). If the site has a search function, use it. If not, try to navigate through product categories.