Put half the mango slices in a bowl with half the lime juice and half the zest, cover and chill until serving. Put the rest of the mango in the freezer for 3-4 hrs or until frozen solid.
Put the frozen mango in a blender with the rest of the lime juice and zest (saving a few pinches for decoration), blend until smooth, then tip into a container and leave in the freezer until needed.
Just before serving, put the chilled mango pieces in the bottom of 6 sundae glasses and take the coconut ice cream and frozen mango sorbet out of the freezer to defrost just enough to scoop. Divide the mango sorbet and the coconut ice cream between the glasses, and decorate with mint leaves, lime slices and any remaining lime zest. Serve immediately.