Ive read that the zapgruder film was edited and the edited version has the car in motion from start to finish.
The real version has the car stopping, then the rifles firing
I hold as plausible that Zapruder made a pause in the interest of preserving a limited amount of footage available; that he wanted the subject closer before committing.
It’s easy to fabricate conspiracies and believe them. A forensic analysis of the original film would easily prove an edit to be true or false, but who would trust even that if it can only be reported by others and not shown directly?