After uncommenting that bit in functions.php, the zlib error is gone.
I've got lost a bit here - which zlib error is this? I can't find a reference in this thread to zlib errors.
I don't think any of the PHP notices mentioned are related. Those are just coding style notices and shouldn't be anything to do with it.
It looks, though, as if the crash is too early for the gzip issue to come into it.
Do you have shell access to the server?
David