After installing the X1 control panel, I was unable to update the Z's firmware.  I tried twice and failed both times.

I then disconnected my G600 mouse and was able to update firmware.  I didn't suspect the G600 at first as I had already updated my work Z and there are 3 mice connected to that computer.

Just a heads up for anyone else if they happen to have this combination of mice and are running into issues.