zJailbreak is marketed as a "third-party application manager" that allows users to install jailbreak apps and tweaks without a computer. It operates as a "donationware" service, meaning the developers request a fee (a donation) to provide a that unlocks the full version of the app.
The most reliable way to find which jailbreak works for your specific device and iOS version. iOS Guide (r/jailbreak)
Here are some possible features that the z Jailbreak Pro freemium code might include: