Why is a CX A340 parked at SYD airport?

Why is a CX A340 parked at SYD airport? I had thought that CX had retired all of the A340's.

I'm pretty sure they use the 340's for HKG-AKL

Where did you see it? Found no evidence of it on FR24, and CX only use their 340's for the AKL route and occasionally on short DOM routes

That A340 was flying HKG to AKL, due to an engine failure. It diverted to Sydney.

btw CX still uses A340 to Auckland and some Asian destinations

Are the Y seats on the A340 still the fixed shell? What a cruel way to fly on such a long route. Does NZ fly its own metal on that route or does it only code share with CX?

Yes they are, 3 hours on the fixed shell Y seats are horrible enough though. That's  why AKL might be the first A350 flight for CX. 

Yes and with the coffin seats in J. 

NZ operates a daily service to HKG from AKL.

The remaining 4 engine aircraft CX operates have the old seats which were pulled from the 777s after complaints. So yes, the hard shell Y and "coffin" J.