This is testable with cheats in a skirmish. My results after messing around for a few minutes:
As far as I know one Trinity should never be able to break an unhindered antinuke, no matter how many missiles you fire.
One Trinity
can defeat a Zenoed antinuke, but you will need to fire many nukes in quick succession (probably at least four).
Two Trinities is a bit weird. At long range the nukes don't spend as much time inside the antinuke's actual firing range since their angle is closer to horizontal, so just firing two nukes at once can score a hit at the close edge of the antinuke's interception radius, or maybe get close enough to kill the antinuke even if the nuke doesn't hit the ground.
When firing multiple nukes from two Trinities at short range, sometimes the antinuke gets confused and intercepts a nuke that is physically closer but further away from impact due to the nuke missile trajectory.
Two Trinities firing one nuke each should comfortably defeat a Zenoed antinuke.
Three Trinities reliably defeats one antinuke.
Behaviour of multiple nukes against multiple antinukes, and attempting to fire a nuke
beyond an antinuke rather than at it or in front of it, is left as an exercise for the reader.