We don’t particularly like the heat, so would you suggest going in March or Sept-Nov? I hear that Jan./Feb. can be pretty hot.
We went in October and overall, had very nice weather. Because of the many places you visit, temperatures can be quite different place to place. Uluru was warm (though just in the 80s for us) while parts of New Zealand's South Island were chilly. It is a great trip - one of our favorites. We have a deposit on the Australia Adventure tour for 2021 and chose an October departure for that trip as well.
We went in early September last year and had good weather. We had a little rain in Sydney and a couple of afternoons in New Zealand. It was early Spring, so NZ was cool, but generally sunny and beautiful. Loved this trip!
I was there late Oct. to early Nov. of 2018. Had only one day of rain, which was in Melbourne. Weather was on the cool side in NZ, but beautiful. This was my favorite trip so far. I'm going back on the new NZ trip this November.