Developer community works hard, sometimes it becomes so useful and one such case is here now. Google Phone v9.0 which has been exclusive to Google devices such as Pixels and Nexus is now available for almost any Android device running Marshmallow or above. The best part, it isn't any zip that you need to flash instead, now what's out is a patched APK which cuts down all the hassle and you can have the newest Google Phone on your device straight away as far as your device runs Marshmallow or above.
To be precise the exact version of this APK is 9.0.154771926 and has been tested with various devices from Samsung, Moto and OnePlus (only those which are running Android Marshmallow or above). Remember if existing name package error appears while installing the APK, you'll have to uninstall or disable the old version of phone app. Here's the file -