Does compression encrease security?

Question

Hi, I have read that compression before encryption increases security. Now my question is: if i decide to compress with zip before encryption, I assume the zip file has a known header saying something like "zip version1". Then the attacker will have the ciphered text plus part of the unciphered text (the zip header). So is it good to zip before encryption? I would like also to ask if the PasswordDeriveBytes() method is good to produce a key and vector (by using GetBytes()on the return value of the method) or should I generate key and vector from hashing the password and getting the bytes from there? thanks, george