Uninstalled Libre Office in Zorin 18 Core, program icons are still in start menu, how do I rid of them?
What format did you install them with?
The /usr/share/applications directory contains *.desktop files which populate the app menu - but these *should be removed on software Uninstall.
So a few questions: Did you install/uninstall from Gnome Software Store?
It defaults to Flatpak on most packages in order to pressure users, especially new ones, into adopting the Flatpak Package Alternatives, instead of the standard APT packages.
You can right-click on the Zorin start menu and select edit menu. Then search libre office at category office and remove the launcher.
Usually the launchers should be removed when you uninstall an app with the software store. Is libre office still shown as installed in software store? Maybe it helps to logout and login again.
Could be assumed OP had Libre Office included as part of Z18 Core install package, so wouldn't that be an apt, same as it was for Z17. (or has that changed for Z18?)
Welcome to the Forum!
You could try the folowing Commands (one after the other):
sudo apt purge libreoffice-common
sudo apt autoremove