Use one wormer or the other...not both. The panacur would be more effective and kill other types of worms if there are any.
Also, no matter what type of worms they are; you're going to have to start a regularly scheduled worming program. This is due to the fact that worm eggs have been deposited...
You have 2 options since you have 2 wormers available: You can use the ivermectin sheep drench by following the directions you posted above. You'll have to dose your rooster 3 days in a row using a syringe without a needle of the mixture. Dose him orally at least 6 times a day, each day during...
Ivermectin has lost its effectiveness as a wormer in chickens due to its overuse as a miteacide in chickens. In otherwords, worms have built resistance to ivermectin, here's a link:
http://onlinelibrary.wiley.com/doi/10.1111/j.1439-0450.1989.tb00635.x/abstract
Covey Rise Plantation is the expert on gapeworms. Here's a link, read posts 13 & 14:
https://www.backyardchickens.com/t/602699/worming-chickens/10#post_7931055