Although by default the DCHP option number sought by the ZENworks Desktop Management Agent is 100, you can change the option number by adding the following DWORD value to the HKLM\Software\Novell\ZENworks registry key at the workstation:
MiddleTierDhcpOptionNumber
You can set the numeric data (that is, the option number) for this value to any number, but you also need to make sure that the data matches the DHCP option string at the server.