hi,
its very simple, just copy your standard BI query to Z, and set the as many as filters from the infocube for your z query.
can be done via query designer tool.
check http://www.sap-press.de/download/dateien/2422/sappress_sap_netweaver_bw_7x_reporting.pdf
Get in connect with BI expert in your team.
Regards
Jansi