If the radical Z contains as substituents phenylethyl, styryl, phenyl, phenoxy, phenylthio- or phenylsulfonyl groups, then said substituents may be substituted by chlorine or bromine, C1 -C4 alkyl groups such as the methyl or ethyl group, C1 -C4 alkoxy groups such as methoxy, acylamino groups such as the acetyl or benzoylamino group, or alkoxycarbonylamino groups such as methoxycarbonylamino or et