I will be traveling to New Zealand and Australia with a cruise ship. Do I need an Australian entry visa and New Zealand entry visa if I already have a UK multiple entry visa?
A UK visa is not valid outside the UK, so yes, you will need visas for both Australia and New Zealand if you plan on disembarking the cruise ship.
Australia, in particular, requires basically everybody except Kiwis to get visas, although for most visitors they can easily by obtained online. New Zealand's visa policy is somewhat more liberal.