It is best to take a train to Zoologischer Garten.

Take the U-Bahn (U 9), direction Osloer Strasse, to Leopoldplatz station.

Change to U 6, direction Alt-Mariendorf The second station is
Reinickendorfer Strasse.

If you arrive at Ostbahnhof or Lichtenberg stations, no problem. Take an S-Bahn train to Friedrichstrasse. Change to U 6, direction Alt-Tegel.
 The fourth station is Reinickendorfer Strasse.
 

Be sure you leave the U-Bahn station by the exit Fennstrasse/Reinickendorfer Strasse. Turn right. Then turn right at the next traffic lights. This is Schönwalder Strasse. The hotel is a few steps down on the right hand side.