You have some issue with one of your Zsh configuration files if that is being displayed just when launching the Terminal. You need to check each of the hidden Zsh profile configuration files.
As for the direct question about getting back to the default macOS PATH.....delete the modified PATH entry from the Zsh profile configuration file since by default macOS has not PATH directly set within the home user folder. The default macOS PATH variable is being calculated/created behind the scenes these days from information located in a system folder (I forget the exact details & location....doesn't really matter because the issue is most likely with your home user Zsh profile files).
FYI, on my M2 laptop running macOS 13.7.1 Ventura, my PATH is:
/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin
I have not modified my PATH although I have installed the XCode Command Line Tools which may have changed it a bit. I don't recall the PATH looking like this previously. I have not installed anything else that should have touched the PATH variable.