Hi,
From my understanding is 4:1 intraday, and 2:1 End of Day.
So as Z8 doesn't close all position should be 2:1

There is this on their web site
"Reg T End of Day Initial Margin 50% * Stock Value"

At the link below:

https://www.interactivebrokers.com.au/en/index.php?f=marginnew&p=stk

And some samples margin calculations below:

https://www.interactivebrokers.com.au/en/index.php?f=marginnew&p=overview3