no way to bypass password.
its not like the key for a safe, if you pass it you get what's inside, the key is used to encrypt the files, wrong key will decrypt file in a wrong way, and they will be unreadable, so winrar will know the password is wrong.
some example about such was is my mobile phone (Ericsson r320), where in the personal codes you set a pin (4 digits) and a check word (3 letters), when you reenter the pin, it will decrypt the database and give you the check word, if it is the same, then you get what you expect, if you enter wrong pin, it will give another check word, and all password are there, but not the correct ones, only with the correct pin it will give correct passwords.

only bruteforce works.
and this is the reason i use winrar to encrypt my important files, as there are no efficient password crackers for it
and bruteforce checks 10-15 password/sec, while zip it check 30 million password/sec.