Hello Jaya,
I found the Australian tour most tiring, but equally enjoyable. It took me more than two weeks to adjust to the time change. The 20 day tour to NZ is a bit different as you travel by a coach while in NZ, stopping every now and then for toile the/coffee breaks, and for sightseeing. You don't have to deal with your suitcase much, it will be delivered in your room and just to need to put it out of the room.
It is tiring to drag the luggage at various airports, wait in the Q, and hang around the airport for hours. I believe this whole routine is exhaustive when you fly around the country.
Dyuti