Zoom F4 Operation Manual page 132

Updating the R firmware
Checking the firmware version
7.
Use e to select Firmware
Version, and press E.
132
(continued)
Updating the firmware
7.
Use e to select Update
Firmware, and press E.
8.
Use e to select "Yes",
and press E.
NOTE
Do not turn the power off, remove an SD card or disconnect
the USB cable during a firmware update. Doing so could
cause the R to become unstartable.
9.
After the firmware update
completes, turn the
R power off.