I agree with coach 723 that you should try using a medicated wormer that has been studied to kill worms in chickens. ZyfendA is not more than an herbal remedy. Products with praziquantel are usually effective. Zimectrin Gold equine paste is one that contains it. Tapes can be difficult to treat, but in my cats and dog who had tapes, praziquantel worked well. You can herbals as a preventative, but when your chickens have an outbreak, it requires a proben remedy.