I also suggest Blackout. It goes perfectly with Zephyr. I LOVE Zephyr but one annoying issue is that whenever you are swiping from a screen with a black status bar to a screen with a gray status bar, it kind of flickers. It looks kind of ugly and annoying. So installing Blackout makes all status bars black and looks fantastic with zephyr! It's kind of strange that blackout is a Mobile Substrate plugin but whatever. I really like how it pairs with zephyr so well. Try it out of you want an always black stays bar!