I see nothing wrong with a long, narrow burst, provided you hit with it. Remember, recoil is your enemy and, if you miss, that's a lot of money being shot away.
In regards to Cyberzombies, they only have so much armor. One good hit should take out its armor, but it still has a LOT of DR dice to play with.
And with vehicles, remember the driver gets to try and avoid your shots as well. I wouldn't use a narrow burst, since you're not doing any damage to the vehicle in any case. But if you do a WIDE burst, then that applies a -9 modifier to the driver's defensive pool, balancing out the -9 recoil you're taking on firing at him. Also, this will work well against your standard KE patrol car (most of the time), but if you're shooting at the big ol' Azzie Cuanmitztli, it boasts a 36 Body and 30 Armor. So you may have taken out it's armor, but there's still two more Complex Actions before you wipe it out with the full auto assault rifle. And it gets to fire back -- BOOM from the main gun and three other weapon mounts.