Disclosed are the combinations containing Z and E stereoisomers of hydrofluoroolefins where the more toxic isomer is less than about 30% weight of the combination (vs the sum of Z+E), to minimize the toxicity impact in the applications they will be used for such as cooling and heat fluids, foams blowing agents or solvents. Also disclosed are means to obtain combinations containing Z and E stereoisomers of hydrofluoroolefins.