When Zak drives the tank past Sarah's trailer, Sarah is wearing a T-shirt. She grabs a pair of shorts and begins to put them on. When she exits her trailer, she's still in the process of putting the shorts on, but now, she's wearing a tanktop she hadn't been wearing before.
After Zack pulls up to the Sheriff's office with the tank, he asks the deputy where the Sheriff is. The deputy says that he is meeting with the Governor. Zack then destroys the telephone call boxes and the patrol car. In the next scene you see the Sheriff talking to the Governor telling him that Zack has destroyed his office, a patrol car, and so on. How would he have know that if no one could call and tell him?
When the tank drives over the police cars at the roadblock, the front end of the tank raises up before it strikes the cars, exposing the fact that a small ramp was set up to aid the tank in climbing onto them.