When using nitrous, the plugs to run are the NGK BKR7E.
NOT the 7E-11's. This is a different plug and while it works for turbos, the plain old 7E's work better for nitrous. Run them a step or 2 colder from stock, depending on how high your shot is. Do NOT run an Iridium, Platitinum or any other -um plug, Just a regular copper NGK BKR7E has been proven to be the most reliable and best working plug for nitrous.

As seen in the first post, ZEX plugs suck. If you haven't had problems with them, consider yourself very lucky. Continue to run them and you will have issues sooner or later.