You cant have both running at same time. They will crash each others requests. You could write your own software that only listens on incoming data based on what Solarpower requests but thats it.
You can have as many connected to a PI as you want but beware of that most serial adaptors are very unreliable long term especially connected to the inverters in this case. I know this because i run 4 of them and they tend to break every now and then. Thats also why i have opted to go for an wireless system based on MQTT instead.
Current setup is based on this code
https://github.com/daromer2/InverterOfThings that i of course forked since i was lazy. But i have big problems with what i call a bug where the ESP ends up in a loop after crash and dont reconnect to the wireless again. Im running the software serial right now and its notorious to be difficult when using wifi at same time but if that crashes i still think it should reconnect but it doesnt.
So if someone with actual mad skills there wanna help feel free to reach out. Backup plan is to go ESP32 and have dual hardware uarts or use the built in HW uart on the esp8266 but that renders current debugging useless unless i use software for that...
It is working though (I havent pushed latest update) with PCM60x/PIP4048/MPI series protocol.