In your zone, you should be able to leave them in the ground. Each old corm will produce one large new corm on top of the old spent and shriveled one and often many little cormlets attached along the sides. It'll take several years for the little ones to reach blooming size.

In a few years, when they start getting crowded, you could lift them and respace them out.

Thanks! I think that I'll leave most of them where they are, since I have a feeling I'll smash the babies, and I'd rather leave them be until they're mature!