I think I mentioned that VB921 part a few pages ago, but its kinda blurry.
Vin refers to the control signal voltage coming from your uP. If you look further down the specs you'll see that it is 4.x to 5.x volts. You'll need a level shifter to go from 3.3 to 5 volts, not to exceed 8 volts. It requires 10ma of signal current to work.
The output stage of this part automatically maintains 7.5 amps of current through the coil. The output stage has a 2.5 volt drop across it. The coil will be ~0.5 ohms. At 7.5 amps thats E = IR = 7.5*0.5 = ~4 volts across the coil. 2.5 + 4 = 6 volts required to operate. This will work with the car battery.
This part that you mentioned in your other post is just about the same as the VB921 part. Either one will work:
**broken link removed**
Vcc refers to the power for the logic built into the chip. It wants to be 5 volts. There is no spec for main coil voltage, but I'm sure its made for a 12 volt system.
A 400 volt zener could be troublesome. The ones I mentioned could flow 6 amps in pairs but that's only for 4 cycles/minute. Your engine won't run that slow
Here is a IGBT coil driver transistor. It has a gate instead of a base so it is a direct replacement for a mosfet. As a bonus, it has its own zener built in.
ISL9V5036S3S
This is an obsolete part but Cross Components in Florida has many of them.