Heads
The anatomy of the heads seems hard to figure. It seems there is no way to connect necks in this manner. However, we don't need necks: Instead we could have each skull connected at the occipital bones, with an extra bone on top to cover it. All of the throats empty into a common pharynx in the middle, and the brains are linked by a ring of nervous tissue
This entire system would be connected to the rest of the body by a standard tetrapod neck, with the gullet and trachea coming off the pharynx and the spine linking to an extra occipital in the rear head
Wings
The wing shoulder joints should be easy to insert under the arms. They can share the major muscles between them, to save complexity
The hands can be added in by a forked wrist joint, with the hand on a palmar fork of the wrist. This is simpler, and should require few extra muscles to move
Feet
The unique feet could be simple to form: Perhaps the heel could be replaced with a cow hoof extending forwards, sat in the arch of the foot. This would quite simply give the desired effect, without much complexity