The version of zmodem I have attached is https://github.com/mecparts/zmp which is re-implementation of zmp based on the last available code release of Ron Murray's zmp.
One of the changes in this reimplemetation is that it does not support multiple ports. i.e. it only supports console and one comm. port.

The driver still supports ability to switch ports (Two comm. ports - A & B) and can be used with the original zmp but both versions do require a separate comms. port for the transfer, separate to the console.