set contour base
set cntrparam linear
set cntrparam levels incremental -10,.1,10
unset surface
set table 'z.table'
splot [-1.2:1.2][-1.2:1.2] \
 'z.fct' matrix us (1.2*($1/50-1)):(1.2*($2/50-1)):3
unset table

#plot './z.opt' us 6:7 w lines, 'z.table' w l
plot 'z.table' w l
