Always verify the MD5 checksum of the zip file if provided by the developer. Downloading system files from unverified third-party websites can expose your device to malware or permanent hardware damage. Conclusion
Fixes for Bluetooth and Wi-Fi stability. Android 7.1.2- Download Zip File
In TWRP, go to Wipe > Advanced Wipe and select Dalvik/ART Cache, System, Data, and Cache. Install the Zip: Go back to the main menu and tap Install . Navigate to your "Android 7.1.2 download zip" file. Swipe to confirm the flash. Always verify the MD5 checksum of the zip
You cannot flash a system zip file on a locked device. Android 7.1.2- Download Zip File