Creating routing file

Ive been playing around with the offline android router
It’s fantastic.
I would now like to swap out the monaco files and insert files for New Zealand which as far as I can tell are not catered for in the demo or hosted on the graphopper site.
I see OSM have some prebuilt files
I have made the routing file using cruiser but I see the demo file ( link above) tries to download a .ghz file, is this some sort of zip file ? and Also while I’m here : thanks, this is an amazing library and very important for the open source mapping ecosystem