I might be totally wrong, but it feels like reimplementing all of vim is not easier that mapping neovim stuff to zed stuff. The author says they would lose it if they embed neovim, but I'm not yet convinced.
Does the zed editor not have plugins?
I have been a vi/vim/neovim user for decades, and I actually use vscode more because of an excellent neovim plugin that does exactly what the author is eschewing: embedding neovim itself.
I have seen so many attempts at trying to include vi keybindings. Mostly, they fall short enough that the attempts are almost worthless. You have to get it mostly right or it fails to satisfy the very people you are trying to lure.
This text - 'asdf-asdf'. If you put the cursor on the hyphen and in Normal mode press dw - in Zed this deletes all the way to the ' and in neovim it only deletes the hyphen, I guess it counts as its own word. Subtle differences like these throw off your muscle memory.
Zed sees that whole string as one word object..
If they add more features, though, they'd have to make sure that they work with nvim. As the amount of features grows, that would become harder.
I would definitely prefer embedded neovim, but I can definitely see why they'd do it this way.