Zeroing external hard drives - does Disk Utility limit you to one at a time?

[Charlie Croker]

Another title explains it all thread. I have two 8TB hard drives, both must be zeroed to make safe before sending off for warranty repair. But Disk Utility doesn't want to let me do more than one disk at a time. Thus I have the first one blanking at the moment for 24 hours then the next one will be due, doubling the amount of time it takes. Can they be done simultaneously? Thanks

 

[GoCubsGo]

Pretty sure you can only do one at a time.