Fair enough. It is a bit of a hack but you could directly access the the library file Zulu uses to store the library list.
Assuming Windows 7, the file is called library.xml and is located in "C:\Users\{username}\AppData\Roaming\NCH Software\Zulu\Library" where {username} is the name of the account you are using Zulu under.
Once the library file is found, open it up and find your desired track. The simplest way would be to search for "<title>Buddy Guy" using the search function based on the track in the image you attached. Near the title there is a set of tags called bpm where you can set the value which is stored by Zulu.
Zulu saves the BPM values when it closes so when you make a manual change make sure Zulu is closed when you make the change otherwise your hard work will be overwritten.
