yikes, again...
i'm sorry, but i'm not really sure what can be done at this point.
believe me, i am sorry if your device is bricked, but i guess that's the risk sometimes. i will say though that we've gotten closer than anyone else has for this thing.
i would say to look for a reset button somewhere on the device, but this will only wipe your data and such if it does anything. i doubt it would reload a standard boot image, but it could.
zte must have found some way to lock down the device against flashing an unverified image. but i'm not sure how. could be proprietary software like samsung use on their devices possibly.
i just can't imagine that it won't boot at all. that seems strange to me, but i don't doubt you.
call straight talk and say it just did that on it's own, ask for a supervisor, complain a little bit, and they'll send for the old one and send you a new one free of charge.
Moderator edit re. the above: modifying your device (i.e., these rooting efforts) and any subsequent negative outcomes as a result of those efforts is clearly above and beyond what the carrier and/or manufacturer intended as normal or expected use that would or should be covered by a warranty return or exchange. The cost, burden, and responsibility of a replacement device should fall on the end user and NOT on the carrier and/or manufacturer for the rooting efforts and risks that you knowingly undertook.
i wonder if we would have modded the default.prop the other way if it would have succeeded. i really wish i knew what it was trying to verify and how it was trying to do so... makes no sense to me.