[Zope] objectValues &c for base class?

If I've got a bunch of ZClasses, all derived from the same base ZClass, is there an easy way to say 'give me a list of all objects whose class or base class is foo'? Sort of like what the current objectValues &c does, but being able to specify the meta_types of the base classes, rather than having to enumerate all the possible different classes. What about if all the classes are in the same Product in Control_Panel/Products? Could you filter based on product? ta, Anthony