Recs.
Updated
Powerlevel9k is an interface for all of the myriad ways in which a zsh shell prompt can be customized, offering even casual users the opportunity to discover the features most useful to them and a quick and painless way to implement them. No need to learn how to construct the prompt directly in your profile, just add the elements you want in simple English to the Powerlevel9k variables and it will generate all the necessary code.
Specs
Pros
Pro Keeps terminal responsiveness high
One sad realization often encountered shortly after testing a new terminal theme or framework is that suddenly a noticeable lag is present when working in it. While it can happen with Powerlevel9k too, if you're deliberate in the elements you place in your prompt, it can also be mostly sidestepped.
Pro Plays well with almost every existing zsh framework or add-on
Powerlevel9k lists step-by-step instructions for integrations into a plain zsh shell, as well as how to intergrate it with: oh-my-zsh, NixOS, Prezto, antigen, Zplug, Zgen, Antibody, ZPM, and zim. No matter what you've already found to enhance your zsh terminal, this theme will complement rather than displace them.
Pro Sensitive to an extremely broad set of contextual environments
Powerlevel is capable of recognizing all of the following conditions and altering your prompt automatically to alert you or provide more relevant information to suit them: logged in as default user, logged in via SSH, low battery, background jobs running, whether the working directory is read-only or writable, VPN in use, operating with elevated privileges (sudo), vi mode (editing), working in a version-controlled directory tree, logged into AWS profile, dynamic display of Wi-Fi signal strength in the prompt itself, current partition free space, and so many more it's nearly obscene.