Its super simple and our FIRST nature is making it more confusing than it needs to be…
If the goal is over the Z1-Z2 line, then common sense dictates that it is in both zones and since one of those zones is the goal scoring zone, then the goal also accrues points.
I do agree though, it would have been clearer if it was written:
*Bullet 3 states: “… the Red Alliance ball scoring zones are zones 1 & 2”
Bullet 4 states: “… the Red Alliance ball and goal zone is zone 2” *
Balls in goals that traverse zones are never counted twice, due to the way the rule is stated (see 1.2.4 in game.pdf): a ball is counted for one point if the conditions are satisfied. It states it in a manner that, to me at least, makes it clear that balls never get counted twice.
Of course, I could be wrong too. I think it would be cool if I was wrong, in fact. I like these strange quirks in the rules.