To be honest, zombie maps are generally ugly and complicated.. I'm personally tired and have some eyes problems, so I can't make waypoints nowadays.. My advice is to read this tutorial (I'll make the same here, later). It will help you for a beginning to gain some skill.

Ps. A nice waypoint file for a medium map, may take several hours to be made and several days of spectating, before to release it as a bug-free & realistic waypoint file.