Hi all, was wondering if someone here could help with identifying a couple of Yak-52s that don't have any clear indication as to what registration mark they hold.

The aircraft I'm interested in are the lead aircraft in this formation with the aftermarket 3 blade prop, and also the blue painted one. The CAA website indicates to me that the blue one is
probably ZK-ZAY, based on the fact that I'm pretty sure that it's based at Pauanui Beach, and the only other Yak-52 based there is -YNZ which is, as you can see from the photo, clearly not the blue one.

If someone could confirm that it is indeed -ZAY (or otherwise) though that would be good. Can't work out which the lead aircraft is; I thought perhaps the "718" may be part of the serial number, as is sometimes the case, but that doesn't appear to be so.
Thanks in advance!