I think this new relationship boils down to one of two possibilities, which explain all the FUD.
Either Zero is already doing well and expanding customers to make more money, or they're in financial trouble and needed this to stay alive. All theories presented in this thread stem from one of those.
Something made Zero do this NOW. What it is, we do not know. The question to ask is, why 10 years? Who most benefits from mandating it be that long?
What FUD? You're misusing the term badly.
As for the deal, there's no reason to read too much into it.
No e-motorcycle maker is making any money (aside from the Chinese ones making 50cc-equivalent e-mopeds & e-scooters).
Sales volume are tiny -- Zero is the largest, and makes in the low 1000s bikes/year. That's not much, and growth is likewise low, because e-motorcycles aren't currently usable for anything except commuting in a way similar to ICE bikes, because of range and cost.
So Zero is simply taking advantage of the opportunity to codevelop & sell drivetrains into an additional market. The "NOW" aspect may be due to Polaris, not necessarily Zero -- we have no idea how long they've been discussing/negoatiating about it.
Energica is doing the same with the Dell'Orto deal.
And as for the 10 years, again, we don't know that it's mandated -- both companies may have exit clauses -- but it seems a reasonable timeframe to develop appropriate drivetrains, and then and then build and sell enough of them to make it profitable. Too short a timeframe would make it much riskier, and much longer doesn't make sense in the automotive sector -- even the largest carmakers don't have detailed projects that are that long, AFAIK. Let alone in the BEV sector.