Is there a one-liner (I'll consider a two-liner for half
price) in VBA that takes two or more collections and forms
their intersection or union?

I know about the Intersect and Union methods, but those
only take ranges as arguments; I'm interested in forming
intersections and unions of collections in general. E.g.,
if X, Y, and Z have been declared as New Collection, I've
added objects to both X and Y, and now I want to quickly
set Z equal to the collection that consists of those
objects that are members of both X and Y.

Thanks,

Robbie