Note: I will assume "Tungtata QCN Tool.zip" is a downloadable archive that contains a Windows tool for working with Qualcomm QCN (Qualcomm Calibration Network) backup/restore files. If your archive differs, the steps below still apply as a general guide for safely extracting, installing, and using a small utility packaged as a ZIP.
If you are a professional technician: Treat this tool like a scalpel – precise, dangerous in wrong hands, but invaluable when used correctly. Always back up the original QCN first. If you are an end-user: Contact the phone manufacturer or a certified repair center. Attempting to fix a baseband issue with random .zip files from the internet is more likely to turn your phone into a paperweight than a working device. Tungtata QCN Tool.zip
Edit: The Tungtata QCN Tool is then used to open that backup, modify the IMEI fields, and save the changes. Tutorial: Getting Started with "Tungtata QCN Tool
The tool is typically part of a larger repair workflow. Technicians often use it alongside other software like QFIL (Qualcomm Flash Image Loader) or QPST (Qualcomm Product Support Tools) to backup an original QCN, modify it with the correct IMEI using the Tungtata tool, and then restore it to the device. Always back up the original QCN first