You do not have to include any amount in your 2011-12 tax return for this demerger dividend component.
TCNZ shareholders are taken to have received a demerger dividend equal to the dividend component of the demerger distribution, in respect of their TCNZ shares.
The distribution amount was NZ$0.4575 per TCNZ share.
This means you received a demerger dividend amount of A$0.3379 per TCNZ share (NZ$0.4575 divided by the exchange rate of $1.3536).
The demerger dividend amount is not assessable income or exempt income.