I'm not a doctor so please don't take this as medical advice, but my understanding is that with an e. histolytica infection, Metronidazole needs to be taken initially to kill the adult form of the protozoa, after which Paromomycin needs to be taken to kill the eggs (and I'm guessing any potential retard generation).
That said, you do *not* take these two drugs together. They need to be taken in succession, with Metronidazole first followed by Paromomycin. I hope this helps!