code: def angle2xyz(azi, zen):
      
      azi = xu.deg2rad(azi)
      zen = xu.deg2rad(zen)
      x = xu.sin(zen) * xu.sin(azi)
      y = xu.sin(zen) * xu.cos(azi)
      z = xu.cos(zen)
      return x, y, z
docs: Convert azimuth and zenith to cartesian.