Diskzero on a large array can take quite some time. However, if you are expecting some kind of DoD level wipe that is not what diskzero does. The ability to recover data has made all software based secure wipes much less effective and no longer used by the government.
If you are concerned about someone recovering data, I would suggest the following.
With the array reset, create a new group. At the CLI use a RAID policy that has no spares. I.e. raid50-nospares. GrpCli>member select <membername> raid-policy raid50-nospares
Let the RAIDset complete. Reset the array and repeat the process using a different RAID level then reset again.
That will be more effective than diskzero.
Social Media and Community Professional #IWork4Dell Get Support on Twitter - @dellcarespro