Pet honesty peanut butter flavored from Chewy. For his weight it is supposed to be three a day but I do two (sometimes three) because it has a lot of the same vitamins that are in his food. His skin is soft and he doesn't itch. I use Wholesomes Sportmix Large breed salmon flavored for sensitive skin and stomach and we haven't had any issues for 3 years. (Chewy or Tractor Supply) I also put a teaspoon of vegetable oil in his supper at least four times a week. I have done that with every dog we have had over 50 years. I think it makes the hair soft.
Let me know how the your vitamin works. How is Zak doing?