Maxwroc, thanks for figuring this out. I successfully flashed the CU9KW this evening. The Tasmota site has some useful tricks which made this much easier and I’ll share for others who might be trying this.
- have an independent 3.3v power supply attached to the ESP8266 instead of VCC from the usb adapter.
- the ground can be permanently connected to GPIO0 during the process.
This means you can set the whole thing up and after connecting the usb you turn on the independent power and it’s read to flash,