well the zn fly for example if you were to buy it at those ratios you would put the following trades on:
+10 zn, -6zb for the zn/zb
-15 zf, +10 zn for the zf/zn
leaving you with:
-15 zf, +20 zn, -6 zb
so it's 10 tics of p&l per 1 tic of movement in the ratio. i have no idea of the margin...