You have zsh set to autocorrect sl to ls even if sl is installed? That seems a bit extreme, is that what the default behaviour is these days? I have all the autocorrection turned off in my setup.
Hmm, on mine (GNU Emacs 23.3.1 on Fedora) it's M-x htmlfontify-buffer. It came with the Emacs distribution as standard. I suspect htmlize-buffer is either from some external package or from a different version of Emacs.