How to avoid for loop?

// how can I do this without for (), by using some functional pattern? How would Haskell do it?

xs = ["a", "Bbb", "ccc", "EEE"]
ys = ["bBb", "DDdD", "eeE"]

zs = xs.map(function f(x) {
  for (var i = 0; i < ys.length; i++) {
    if (ys[i].toLocaleLowerCase() == x.toLocaleLowerCase()) {
      return ys[i]
    }
  }
  return x
})

// expected result: zs = ["a", "bBb", "ccc", "eeE"]