Using zsh autocompletion for alias

Try looking up zsh abbreviations. They allow you to enter an "abbreviation" which automatically gets replaced with its full form when you hit a magic key such as space. So you can create one which changes ...<SPACE> to ../...

For example, this is what you need in your profile:

typeset -A abbrevs
abbrevs=(
        "..." "../.."
        "...." "../../.."        
)

#create aliases for the abbrevs too
for abbr in ${(k)abbrevs}; do
   alias -g $abbr="${abbrevs[$abbr]}"
done

my-expand-abbrev() {
    local MATCH
    LBUFFER=${LBUFFER%%(#m)[_a-zA-Z0-9]#}
    LBUFFER+=${abbrevs[$MATCH]:-$MATCH}
    zle self-insert
}

zle -N my-expand-abbrev    
bindkey " " my-expand-abbrev 
bindkey -M isearch " " self-insert

To request that a command be completed like another command that is already known to the completion system, you can use the compdef my_command=known_command form of compdef.

compdef s=ssh
compdef {cxterm,uxterm,xterm-color}=xterm

Under the hood, this is basically equivalent to _comps[s]=$_comps[ssh].

Some completion commands apply to a family of functions and read the first word of the command line to determine which particular command to complete. For example, the commands ssh, scp, sftp and a few more are all completed by the function _ssh. In that case, you need to tell the completion function which “service” your function is like (by default, the service is the executable name, here your function's name).

_s () {
  local service=ssh
  _ssh "$@"
}
compdef _s s