Most Australians have never seen a Platypus in the wild.... so yes, a zoo is the go there... As it is for many other smaller native animals...

Id be surprised if you didn't see Eastern Grey Kangaroos just while driving outside of towns.... that's the second largest species and they can get quite large....so that should tick the "Kangaroo" box nicely...
There are only three species of snake in Tasmania...and they are all venomous....so.......seriously... don't be concerned by the apparent number of dangerous animals.... be sensible yes... but no need to worry unduly....