So if your vet is SURE that this snake has hookworms, then metronidazole would seem to be the wrong drug for the job. See my post #64 above.
And by all means, do your own reading up on treating hookworms effectively in snakes. I don't find Metronidazole recommended anywhere for hookworms.
I'm not a vet but I can read. And WOW, that was a LOT of Fortaz! I've never used it & haven't researched that specifically (yet), but antibiotics in general are rough on a snake's body, & every 3 days for 2 months is a long time. It would be a miracle if he WASN'T regurgitating after killing off his gut bacteria so effectively.