If someone sends me a zipped file (non encrypted through email) and I want to forward that same file to someone (but I want to encrypt it in an email), when I send the email PKZIP does not ask me to enter a password or give me the ability to encrypt the file. Is this a bug and/or is this normal?
I'm pretty sure this is normal. You have to explicitly/manually create the Zip file with a password, or add the password after the fact (which sometimes only password protects files added after that).
If you are simply forwarding a Zip file you received in email to another user (all within your mail program) then the email program will simply reattach it as-is.