Yeah I accidentally ordered it up front, I was just checking the value converted prices in Paypal and hit this button:

I did not think "continue to review" would instantly confirm the order, so I suppose it's a possibility that I'll just have to swallow the full shipping cost. I've reached out to support on if it's possible to get them combined for a partial refund on the shipping fee, hopefully they'll be able to help.
At least it seems like it was the last Scarlet left, so I'm only slightly upset with Paypal for this misuse of "continue to review".
Edit: It was no problem, they'll combine the shipment and upon re-calculating the cost, refund me the difference. ZMF support once again coming out exceedingly positively.