Herbicidal diphenyl ethers and their use for controlling undesirable plant growth

A diphenyl ether of the formula ##STR20## where Z.sup.1 and Z.sup.2 independently of one another are each hydrogen, halogen, nitro, cyano, carboxyl, C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -haloalkyl or C.sub.1 -C.sub.4 -alkoxy, Z.sup.3 is halogen, nitro, cyano, C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -haloalkyl, C.sub.1 -C.sub.4 -alkoxy, C.sub.1 -C.sub.4 -haloalkoxy, C.sub.1 -C.sub.4 -alkylmercapto, C.sub.1 -C.sub.4 -haloalkylmercapto, C.sub.1 -C.sub.4 -alkylsulfinyl, C.sub.1 -C.sub.4 -haloalkylsulfinyl, C.sub.1 -C.sub.4 -alkylsulfonyl or C.sub.1 -C.sub.4 -haloalkylsulfonyl, and R is, halogen or --X--R.sup.1, where X is oxygen or sulfur and R.sup.1 is hydrogen, C.sub.1 -C.sub.20 -alkyl, C.sub.2 -C.sub.20 -alkoxyalkyl, C.sub.2 -C.sub.20 -alkylthioalkyl, C.sub.2 -C.sub.20 -alkylaminoalkyl, C.sub.3 -C.sub.20 -dialkylaminoalkyl, C.sub.1 -C.sub.20 -haloalkyl, an unsubstituted or halogen-substituted phenyl alkyl radical of 7 to 9 carbon atoms, C.sub.2 -C.sub.8 -alkenyl, C.sub.2 -C.sub.8 -haloalkenyl or C.sub.2 -C.sub.8 -alkynyl, carboxyalkyl, alkoxycarbonylalkyl or carbamylalkyl of not more than 6 carbon atoms, cycloalkyl of 3 to 20 carbon atoms or unsubstituted phenyl or phenyl substituted by halogen, C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -haloalkyl, cyano or --O--(CHR.sup.4).sub.n --COOR.sup.5, where R.sup.4 is hydrogen, methyl, ethyl or propyl, R.sup.5 is alkyl of 1 to 4 carbon atoms and n is 1, 2, or 3, R is --NR.sup.2 R.sup.3, where R.sup.2 and R.sup.3 are identical or different and have the meanings stated for R.sup.1, or if R.sup.3 is hydrogen or C.sub.1 -C.sub.4 -alkyl, R.sup.2 is hydroxyl or C.sub.1 -C.sub.20 -alkoxy, or is C.sub.1 -C.sub.20 -alkoxy which is substituted by C.sub.1 -C.sub.6 -alkoxy, C.sub.1 -C-.sub.6 -alkylthio, C.sub.1 -C.sub.6 -alkylamino, C.sub.2 -C.sub.6 -dialkylamino, halogen, carboxylalkyl, alkoxycarbonyl or phenyl, or is unsubstituted phenoxy or phenoxy substituted by halogen or C.sub.1 -C.sub.4 -alkyl or unsubstituted, C.sub.1 -C.sub.20 -alkyl-substituted or phenyl-substituted amino, or R.sup.2 and R.sup.3 together with the nitrogen atom to which they are attached are azetidino, pyrrolidino, piperidino, morpholino, 2,6-dimethylmorpholino, piperazino, 2,6-dimethylpiperazino, N-methylpiperazino or N-ethylpiperazino .