Modifying your device's software carries inherent risks. The author is not responsible for bricked devices, lost data, or nuclear war. Always verify checksums (MD5) of downloaded files before flashing.
If you search for a generic .zip file to install on any phone, Android does not work like Windows. Every device requires a specific build of 5.1.1 compiled for its processor (chipset). android 5.1 1 update download