Quite a number of us in seasons past have had Zucchs growing but not maturing fruit. Many solutions have been advanced! Lack of pollination, too-wet-too-dry, not enough Calcium in the soil to name a few. Crinkly leaves - I read about this relating to Capsicums and it was not enough Calcium (Gypsum, Dolomite). If you read Linda Woodrow's blog (right-hand side of this forum front page) she had stopped trying to grow Zucchs and grows Trombonchino instead. I have some seeds and will happily post them to you if you'd like to try them.
hmm. I don't know - this has never happened to me. I had a quick google, didn't see any answers - several of the same problem though.
See that brown scorching and mottling on the old leaf at the bottom? Classic potassium deficiency signs. Potassium is important for flowering and fruiting - so that could well be the culprit.
I suggest chuck a few handfuls of ashes from the fire around (or a kitchen scrap compost - make a tea for a quick hit maybe). Maybe shallow bury a couple of banana skins as well, for slow release potassium.
As to why this might be a regional problem? Not sure. Have you had a lot of rain in the Central Qld region in the last couple of months? (I gather it's been very dry in Brisbane). The Permaculture manual says potassium deficiencies are common on "leached acidic or organic clay soils".
The leaves do look a little pale - usually a symptom of acid soil - it might be a good idea to add a bit of lime or dolomite as well.
If it is potassium, it should perk up pretty quickly if you give it a hit - my broad beans came good within two days of being ashed :) (water in of course)
Thanks Elaine & Scarlett, will try the wood ashes Scarllet & we certainly have had unusual rain for the winter. Yes please Elaine I would like to try the Trombomchinio, I usually read Linda's blog but had not noticed anything about the Zucc problem. Let you know the results.