Actually, you can specify a pass with nothing but zeros using the tool I mentioned.
However, I will likely repeat myself in saying that exists at least one reason not to adopt a single pass with zeros.
If you are trying to make the other partie's life as difficult as possible, I would like to see many random characters added. In fact, I would welcome that one of these tools would throw a few fake file headers in the process, just to make the resulting disk so garbled that causes the forensic efforts some frustrating hours. It is no personal attack against forensic professionals, I'm just safekeeping my data and adding some traps for the preying eyes.