Mapping problem

problem.ts

fromThis = [
    {
    name: 'A',
    child: {
      x: "X",
      y: "Y"
    }
  },
  {
    name: 'B',
    child: {
      z: "Z"
    }
  }
];

toThis = [
  {
    name: 'A',
    child: "X"
  },
  {
    name: 'A',
    child: "Y"
  },
  {
    name: 'B',
    child: "Z"
  }
];