Hello ObliqueGeek,
with a third party app, this can be done SBZ , we can achieve this and our team would be more than happy to set this up for you . we can also manage all kind of shipping based on different condition you can check the full list and Review of app here :https://apps.shopify.com/shipping-based-on-zipcode
if you are facing difficulty setting up the app then you can just contact customer support and they will help you out with this .