If Zeiss is charging $178 for service, that's pretty reasonable. Sure, you'll get a local shop to probably do it faster and maybe slightly cheaper. Definitely an alternative if you have someone you know does a good job. But if you don't, sending it to Zeiss doesn't seem like a bad idea.
Will be interesting to see how long it takes to be serviced in Germany (vs. Leica's glacial turnaround times).
As for whether or not the Thornwood address is correct... it seems clearly the one to use based on the
Zeiss service webpage. Sorry, no firsthand experience dealing with them, yet (so far my ZM lenses have not required it).