The "z" at the end often signifies a development build , a private patch , or a beta version that follows the stable 3.5.1 release. Similar Scientific/Technical References
In technical and medical literature, "3.5.1" frequently appears as a section header for specific data reports: Heist Editor 3.5.1.z...
There are various "Heist" related editors used for game level design or character customization (e.g., for games like Payday or GTA ). If this is a modding tool, version "3.5.1.z" would be a very specific development branch. The "z" at the end often signifies a
This is for informational purposes only. For medical advice or diagnosis, consult a professional. AI responses may include mistakes. Learn more User's Guide for the AMS/EPA Regulatory Model (AERMOD) a private patch