digraph iumlaut {
  rankdir=RL;
  node [shape=plaintext width=0 height=0];

  i1 [label=i];
  {e y} -> i1;
  {o ə æ} -> e;
  a -> æ;
  u -> y;

  i2 [label=i];
  {ui ei} -> i2;
  ou -> eu;
  {oi eu æi} -> ei;
  au -> æi;
}