ok, so before you do anything else it maybe worth raising a NetApp support case to look at those drives flagged as failed.
if the disks are part of an aggregate then they can't be zeroed anyway, they would have to be removed from the aggregate, the only way to do this is destry the aggregate unfortanately.
so maybe need to go back to the start and ask, what is it your trying to do, why do you need to zero those disks?