Prepare. In a bowl, set strawberries and mango. For a smoother texture, lightly crush the fruits with a fork. Add sugar, juice and lemon zests. Cool down for 15 minutes. Gradually pour pectin over the fruits by stirring with a wooden spoon. Mix non-stop for 3 minutes.
Freeze. Divide the jam into jars by filling them up to 1 cm (½ inch) near the rim. Wipe edges of the jars and close the lid. Cool down 30 minutes at room temperature before freezing. Those jams can be frozen up to 6 months.
Defrost. The night before, let the jams thaw in the refrigerator. Once thawed, the jams may be kept up to 2 weeks in the refrigerator.