So who manufactures these cars?

They can be found at Toys R Us in the r/c car section. They are called Xtrek Pro. I hate mine. I will return it asap.

Are they really faster than a zipzap? I got a Cadillac Escalade Zipzap and it was fast until the battery wore out from charging too much, I replaced it, but it still goes too slow.

Well, I had a pretty fast Zipzap, but for stock yeah they are faster. They have proportional steering (I guess). I hate mine I like my zipzap WAAAY better. It may not have proportional steering but at least its driveable.

ZipZaps SE have Digital Proportional steering with the option of head and tail lights. But the car body looks a little chubby on the Xtrek. The thing that is cool about a zipzap is they are more realistic looking. My friend once stole my Black Escalade on a SE chassis. He thought it was cool since it had lights, played 2 tunes, and had proportional speed/steering. Now I use the new chassis from the CARS movie. They are faster no On/Off switch and they still have lights the Escalade body still plays music on it. It stinks they don't make anymore Zipzaps.

The proportional zipzaps were slower than the non prop ones due to weight (I think).

I would say weight too, But if you had a Oral B ToothBrush that vibrates, take it apart and take the motor out, then take that metal vibrating thing out(The Little Stick also comes out), and take apart a stock Zipzaps motor and use the stick from the zipzaps motor and put it in the Oral B toothbrush motor and your car goes very fast. The Non Prop ones went faster than the Prop ones even if the Prop Ones had a NX motor. Plus add a second battery to that oral B toothbrush Zipzap on a non prop and the car would go zooming fast, but flips over way too much.