w4mmp:
I can't image why Zen Cart does not have that as an option somewhere.
Two words spring to mind. "User Interface".
Seriously, what you are seeking isn't going to be *particularly* hard to achieve with code edits that can be made to alter the program flow/behaviour based on specific products or categories, but because every Zencart installation will have different products/categories, what mechanism do *you* see that would not only allow the easy 'tagging' for these products/categories, but how or where would you define the actual actions needed when they are identified?
If you search these forums you will find *many* practical examples as to the type of edits needed for this kind of thing - but ultimately, they are all specific (or need to be customised) for any given store due to the way the individual stores are configured, and the customers own specific needs and requirements.
I imagine that any 'user interface' that could handle these needs would probably end up being more complex to use than the code editing method. I could be wrong, but my mind boggles at the thought of even attempting to create such an interface.
If this in itself wasn't hard enough, for your needs you are going to need a major rewrite of the entire way that zencart handles the shipping - because 'internally' there is no mechanism to sum the shipping totals of a cart that contains products that need alternative shipping methods. - and should someone actually make this possible, I then wonder how these quotes will be presented to the customer (and recorded in the database so the merchant knows how the quote was derived). Again, this comes down to a 'user interface' issue.
This is one of those things that appears trivial on the surface, but as you dig deeper into it you will (hopefully) realise involves a lot more than you've already imagined.
Cheers
RodG