With respect to Zealandia, it was formed by oceanic seafloor spreading aka expansion/growth just as all continental crust formed and just as basalt pillow lava and oceans form now.
Zealandia is young (that pesky old core sample and zircon dating thing). It didn't exist in the Jurassic and was formed in the Cretaceous, when, according to plate tectonics dogma, there were no land bridges.
Score another loss for plate tectonics.
Expanding Earth 1-Plate Teconics 0
Wegener, A.L., The Origin of Continents and Oceans, 1915
Mortimer, N., Zealandia, ASEG Extended Abstracts, 2006
And OIM Looses again.
I have a Jurassic fossilized fern sitting on my desktop that says you're wrong.
Not to mention the fact that I know for a fact that there are dinosaur fossils right here in New Zealand.
Not to mention all those pesky andesitic volcanoes - and the ruddy great hole in the middle of one of the islands (here's a clue, those sorts of holes don't tend to form with basaltic volcanoes, and basaltic volcanoes in the southern hemisphere don't tend to erupt with such violence they cover 10% of the southern hemisphere in half an inch of ash, and inject that much ash into the atmosphere that the effects of the eruptions are record by the chinese and romans.