Answer:
Wonder Woman was granted a number of special gifts and powers at the time of her birth. Among flight, speed, wisdom and others, the gods granted her the 'strength of the earth'. When asked about her strength, Diana herself commented that it was difficult to find weights heavy enough to challenge her making her limits hard to determine. She has been shown to be stronger than a fully mature martian like Martian Manhunter, and is known to be 'stronger than Hercules' which puts her above Shazam/Captain Marvel as well. She is likely the most physically strong of all the DC heroes second only, perhaps, to Superman (whom she has fought to a standstill on several occasions).