The stadium would be a ULURP action regardless of the zoning district. If an agreement could not be reached, it wouldn't be impossible (or significantly longer), to include a zoning map amendment to change the C4-4 district to a comparable district without an accessory parking requirement for a stadium (e.g., C4-5). The site is large enough that it would not be a "spot" rezoning and it could bypass specific parking requirements. The special permit does require review of vehicular access and traffic, but that could be manipulated and there would be more freedom for off-site parking options.
It is frustrating to read about parking again in reference to a potential stadium, but long term the stadium has support (City and State), whereas the casino does not, regardless of Hochul's appearance at a Mets game. If I had to wager, Cohen loses this one.