A better take would be the mechanism of action on creating an immune response that targets ZP, takes a similar schedule.

There is no PZP in the vaccine and PZP doesn't seem to be inhibited by Ivermectin, since that would be noted on horses pretty quickly and widely.

But that doesn't mean PZP research didn't contribute to vax research in some way.

Finally, multiple layers of 'security' is better than 1 or 2, I think the people doing this knows they won't get a 2nd shot, pun intended, at mass depopulation and would logically stuff as many mechanism as possible in the shot.