Stupid question re Amazon returns

[BruceAndNosh]

Surprisingly, I have never had to return anything to amazon.
However I have just ordered an item and an accessory for it that I will have to return as I found a more suitable item in store.

Both items arrived together in the same box.
I have opted to return via Post Office "Box required, no label needed"
I have been sent two separate emails with QR codes to show at PO who will print my label/ labels.
Can I pack up both items together in the box they arrived in or do I need to provide 2 separate boxes?

I don't want to be turned away for having pack them wrongly

Many thanks

I’d do it separately.
If only one is scanned somewhere on the journey, you might not get refunded for both & I imagine it will a lot of effort to sort.

Thank you, I'll get another box