Have you enabled the Zsh shell as your default Shell, and configured a ~/.zshrc file in your home directory? Also, note that Automator is a cascade of arguments from one action to another and doesn't know the PATH that you have setup in your Shell dot file.
So launching the PowerShell application and then using a Run Shell Script action won't do a thing for you unless you are passing arguments to the Zsh shell and processing those arguments in a Run Shell Script script. Pretty sure that the Run Shell Script does not offer PowerShell as one of its Shell arguments.
You will likely need to create a HERE document in that Run Shell Script that invokes PowerShell to run the associated HERE code as in this example using Python3 from a Python.org installation:

Since this was coded, the Shell: options now include this /usr/local/bin/python3 and the HERE syntax is no longer needed. You would not need to have a preceding action to launch PowerShell when used in this manner provided that PowerShell supports this form of invocation.