The Zuma of course has 2 headlights but only 1 runs at a time. There is 1 for Low and 1 for High. I have never had a problem with the lights. In my opinion they put out enough light.
BUT...the 1st mod that most Zuma owners do is the dual headlight mod which lets both headlights run at the same time.
Here is a link to the thread to explain it all.
The stock lights put out 55 watts on low and 60 watts on high.