Post #5 and #8 are the correct answers.
Your system does not have the unzip program installed. Yum is the RHEL package manager, and should be used for tasks like this. However, YOUR yum is broken, it is saying there are no available repos, and that's the heart of your problem. This is what you should be investigating, once it's resolved installing unzip is trivially easy.
So, why do you not have any repos? Have you been hacking at your repo list for some other reason? Following some unmentioned guide somewhere that borked your yum setup? Do you not have a valid RHEL subscription?