The easiest way to get your Zarch adf file running on a Pi is to launch ArcEm and then run it through that. It works perfectly.
Im sure getting it running direct through jaspp is possible (I think I've done it, can't remember) but your best bet is to as Sirbod/Jon Abbott (the guy who authored jaspp) on the stardot forum or the jaspp one.
http://forums.jaspp.org.uk:9000/forum/