I honestly did not realized 1.7 was unsupported. I just went to oracle's java website and downloaded the most recent version. Zenoss is not complaining in either of my core 4 environments that are running 1.7 and I am monitoring some servers via jmx.
What installation guide did you use? I was using Zenoss_Core_Installation_01-012013-4.2-v09 that i felt did not have all of the correct manually installation instructions.