Sure, I understand that, it's just this was my own opinion of how I like to play Zac. It's just full tank scales best. I rarely build AP items myself. It's just that in isolated circumstances, it works. I probably use Rylai's in 1/100 games.

Zac has an extremely large amount of sustain on his own. Usually, you are able to just use 2 potions on first run. Honestly it is take it or leave it with it because you will never die in your jungle. Also, another point is that bonus health will, of course boost your regen.

Strength of Ages + Veteran's Scars collect huge amounts of health that benefits you through all stages of the game. Bonus regen would save you 50 gold so you can use 2 pots.

Hey, first off this is a very nice guide, and I don't have much to suggest ^-^. On the item side of things, while Rylai's does give the stats that Zac needs, because all of his attacks are AoE its effect isn't really used to its full potentioal. While the stats given by Liandry's Torment aren't quite as good as Rylai's Crystal Scepter stats, if you're only building one AP item then I think that it works with Zac's kit better overall. Slowing with q and hitting a group of people with any other skill effectively applies an AoE Double strength Liandry's passive on top of, for instance, your percent damage on your w. Since Liandry's adds % damage as well as a decent chunk of AP it gives a good damage spike to Zac, without really sacrificing the HP that he needs.

The only other suggestion that I have, is taking Runic Armor instead of Veteran's Scars . This buffs your blobs to giving 4.32% max hp back right off the bat, increasing to ~5.12% when Spirit Visage comes into the mix.