With 31 species in their collection, they lead the next best Australian institutions (Perth on 24, then Healesville and Currumbin on 23) by a country mile. I'm willing to say with 99.9999% confidence there is no zoo outside of Australia that can top this. Halls Gap Zoo has the widest collection of marsupial species in the world.
It certainly sounds impressive - I hope that a) you aren't just being paid by them to promote the zoo
Tasmanian Devil
Dingo
Feathertail Glider
Squirrel Glider
Spinifex Hopping-Mouse
Eastern Grey Kangaroo
Kangaroo Island Kangaroo
Red Kangaroo
Western Grey Kangaroo
Koala
Common Brushtail Possum
Common Ringtail Possum
Northern Quoll
Eastern Quoll
Spotted-tailed Quoll
Yellow-footed Rock-wallaby
Brush-tailed Rock-wallaby
Parma Wallaby
Red-neck Wallaby
Swamp Wallaby
Tammar Wallaby
Tammar Wallaby SA Mainland
Agile Wallaby
Common Wombat
Southern Hairy-nosed Wombat
Bilby
Red-tailed Phascogale
Red-bellied Pademelon
Long-nosed Potoroo
Brush-tailed Bettong
Southern Brown Bandicoot