Now that you know about ci(, I highly recommend taking a look at tpope's plugins. Especially the surround plugin. It can change the surrounding parentheses and tags (if you're editing an HTML or XML document). Quite cool. Also, there's much more in tpope's library of pugins.
PS, did you know that zsh has a vi mode, where you can use typical vi commands to edit the command prompt instead after the default ones? Quite useful as well.
If you're going to check out zsh, make sure to take a look at oh my zsh! There's a lot to explore there, but the plugins are cool.