Conversation so far:
What types of things has Sylvester Stallone done other than act?
Sylvester Stallone made his directorial debut and starred in the 1978 film Paradise Alley.
Who else was in the movie Paradise Alley besides Sylvester Stallone?
Armand Assante appeared in Paradise Alley. Anne Archer also starred.
Was the film Paradise Alley a success?
Paradise Alley received negative reviews from many critics.
Is directing the only type of thing Sylvester Stallone has done, other than act?
In August 2005, Sylvester Stallone released his book Sly Moves.
How did the book Sly Moves by Sylvester Stallone do?
What types of advice did Sylvester Stallone give in his book Sly Moves?
Sylvester Stallone's book Sly Moves claimed to be a guide to fitness and nutrition.

Question: What was his biggest success as a director?
Self-contained rewrite: What was Sylvester Stallone's biggest success as a director?