Honestly you probably can do these with bash as well with some tweaking. But on a daily basis these are most used by me

    auto_pushd

Replaces internally cd with pushd (plus a few more: to ignore dups, be silent about it).

Global aliases (interpolated anywhere in the commandline)

    alias -g G='| grep -i'
    cat file G something

Replace on the fly long directory names with short paths

    /some/long/path $ export X=`pwd`
    ~X $ 

All the tweaks to ignore dups in the history, when saving/searching.