I've never tried either of those, but it never hurts to try. Threadleaf's skinny stems might be challenging to root, but no experience here. Generally something to hold humidity around any cuttings increases success.
I don't have Zagreb but I think it's much like Moonbeam, which is very easy to divide. I don't even dig up Moonbeam to divide. I just stick my perennial shovel down through the plant, then dig up the portion I plan to move. Snapdragons propagate themselves well around here; I just let them reseed.
I do love my perennial shovel. It looks like this
http://www.gardeners.com/Peren...
Karen
