They have numerous spawn points all over the hill giant hill and around the ruins at the base of the hill (/waypoint 2812, -1945.) They path south from the hill into the canyon, then west, then north to the Inns. They walk back the same way they came and then despawn after a few minutes. The best place to wait for them to spawn is where the canyon opens up to the hill giant hill (/waypoint 2004, -2316.) If you don't have tracking I recommend waiting in the canyon because if you're on the hill a spawn may pop near the ruins and could walk by without you seeing it.
Hasten Bootstrutter stops at 4421, 1510, 4.17 and -166, -78, 2.66 for around 1 minute each, before despawning at 1593, -2431, 1.6
Brother Zephyl stops at 4290, 1460, 6.72 and 1016, -41.5, 11.96 for around 30 seconds each, before despawning at 3160, -3436.5, 2
The blue circle in this picture represents the area where they spawn, and the blue line represents the path where they roughly walk. Hasten Bootstrutter walks further south, but Brother Zephyl sticks pretty close to the blue line, except for despawning more Northeast.
Factions
None for Hasten Bootstrutter, good luck killing Brother Zephyl.