When Hercules battles the Nemean lion, the lion's head alone appears to outsize Hercules entirely, yet the scale of the lion headdress that he wore after slaying the beast is much smaller in comparison.
In Greek mythology, the god Zeus is the father of a child named Heracles, not Hercules. Hercules is the Roman name and the divine father is called Jupiter. The film producers probably used the name Hercules because it is better known that Heracles.
Some close-ups of Hercules facing Rheseus' army have been flopped. The rectangular Thracian shields have a space top-right for a spear but in at least two shots the soldiers behind Hercules have a space on the top-left of their shields.
After Hercules saves his companion from a flaming spear, he throws a soldier down a hole. When said soldier hits the rocks before falling down, you can see the prop rocks shrinking under the stunt actor's weight.