wow, it's a kind of magic! after so much hasle and forum pages, I'm so sorry to bother, thank you so much whim, smartkiller and everyone else out there working on CHDK.
I've tested the optical zoom while recording and it works great!
Is there any other trick that I should know by now?
Next time I download the latest trunk, I just need to swap the disk and replace the bin file with the new one?