In both bash and zsh, you can force the shell to use $PATH for lookup (bypassing functions and shell builtins) by calling a builtin name with 'command' ('command time -l ls'). You can equivalently force a builtin with 'builtin', but that does not work with reserved words (and 'time' is a shell reserved word).
Yeah. Shell semantics can be pretty unintuitive sometimes. I often find it helpful to translate these ideas to standard programming language terms.
* Commands are like functions
* Commands in /bin etc. are like library functions
* Builtins are like a language's primitive functions
* Keywords are keywords
