A rather odd story, granted from the Mail. Apparently Zaha asked to be left out of the latest squad because he gets homesick on the international breaks.

[Link]

'He asked not to come because he becomes home sick at each break,' said Beaumelle after announcing his squad without Zaha in it. 'He wants to reflect on the rest of his international career.'

Hopefully this ends up him not getting picked/deciding not to go to the Africa Cup of Nations

Probably his agent trying to make him more attractive to buyers e.g. he wont disappear in January.

One more point

I read on Twitter that what he actually said was he comes home sick from every international trip.

Sounds more likely a reason than him being homesick.

Some people think football is a matter of life and death. I don't like that attitude. I can assure them it is much more serious than that.

Let's hope we never qualify for Europe.

Or that he ever joins that elusive Champions League team.

Whatever next haha

The cynic says that he wants to be available for sale.
The generous side of me says that he is enjoying playing so much now that he wants to stay and help Palace climb the league table.
The generous side of me won the argument easily!