China dwarfs Iran: about 9,371,225 km² km² against 1,622,847 km² km². At true size China is about 5.8× larger — the whole of Iran fits into China roughly 5 times.
Both sit in Asia, so this is a same-region comparison: the new Equal Earth map draws both with the same honest geometry, and the real gap is exactly the 5.8× you see above.
The old Mercator map treated both about equally (1.6× vs 1.4× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Iran fits 5× into China.