My understanding is that H. sinuata has yellow forewing markings, and H. coryphoea has white forewing markings, and the hindwing markings of both species vary more than the difference between the species.
'in H. coryphoea there is a black patch below the apex that reduces to a narrow black line extending along the trailing edge to the tornus; in H. sinuata there is a similar black patch below the apex but another black patch just inside the tornus, with a black line along the remainder of the trailing edge.'