I love your idea! I may have to try it this weekend when I play some games. Here are my thoughts / questions regarding it.
Which jungle enchantment is that?
Liandry's is perfect for this, it adds a lot of damage for him because he has so much disruption. If you want to go ap bruiser / add damage that is the first item you should get towards damage. I would even get it in the jungle.
is a fantastic Item for Zac, no matter what build he is going. The increased healing is just awesome with his blobs.
I don't think Zac would need a zhonyas because the immunity just keeps him from continuing to cast spells in a fight.
Something to consider is Twin Shadows because of the movement speed and the active can help you to catch targets and prevent them from juking your slingshot jump. Also that slow can help count for cc to up Liandry's torment damage if you use w and your other spells are on cooldown.
I don't see the use of this, Zac already has plenty of engage and cc. If you were going for burst damage then maybe... but only if you stacked health, at which point you'd be building tank.
The immolate passive of these items helps add DPS, and synergizes with
so you might want to consider getting one of these too. If you go top you could even substitute Sunfire Cape for Dead Man's Plate in your build.
You could also consider building this on your top build, it's not necessary at all. If you are trying to fill item slots it does provide both health and ap, which are stats that bruiser Zac can use.
These opinions are my own, and I do not claim them to be fact. They are just what I believe.
Regards,
HalcyonDweller