7
I think the change from Rufi to Luffy is acceptable. In that case, it's meant to be pronounced as something to close Luffy, while in Zolo's he is meant to sound like Zoro with a soft r, as a throwback to Zorro.
The wiki cites that Zoro was named Zolo not as a pronunciation move (well, it may have been), but because of copyright issues with none other than the person he was meant to be an homage to, Zorro.
Though, Derozio, you should be fine. The first few volumes apparently have Zolo as Zoro, and they...for some reason...started to use 4Kids names more and more(though don't quote me on this).