R&S VNA ZVRE 1043.0009.50 Firmware

[BoscoLab]

I am looking for the firmware for a ZVRE 1043.0009.50. The VNA is currently equipped with firmware 1.70. I think this is still the DOS version. I have checked which CPU is installed. It is a Pentium with 133 MHz.
I could not find a download for a firmware update. Who can help and has the appropriate updates on disk? Which version is best for the ZVRE 1043.0009.50?

Thanks for your help. 

PS: I make a backup of the hard disk and replace it with the CF card.