Why don't you just purchase some enzymes and take high doses of them. It appears that Zymex is just enzymes. You can get enzymes anywhere. If you are taking a parasite cleanse and it doesn't appear to work probably is because you are not taking a high enough dose. Also, I work in a place where they test feces for parasites.
Many, many people send feces there with these "strings" that they suspect to be parasites. Roughly 95% of the time these "strings" turn out to be nothing more than mucous with feces attached to it.
We did get one worm in from an older lady and turns out it was insect larvae as if she'd spent too much time gardening while sitting down. I have seen worms, I mean worms. These are fat, pink and tapered at the ends. They usually come from kids for some reason. I don't know if it's because they walk barefoot, play in the dirt alot or just unaware of hygiene.