Replace File Manager

[Aravisian]

That is a command to restore Nautilus.
Try this post, instead:

How do I change or delete the default file manager (Nautilus)?

I also use Nemo (In fact, I use the Cinnamon desktop) on Zorin. You cannot remove Nautilus from Zorin Core as it is integrated into the desktop. But you can make Nemo the default: Once you have Nemo installed, please run the following in terminal: xdg-mime default nemo.desktop inode/directory application/x-gnome-saved-search gsettings set org.gnome.desktop.background show-desktop-icons false gsettings set org.nemo.desktop show-desktop-icons true