Not the buff Zac needs, but the one he deserves.
Zac, like a few other champions, have some sort of mechanic involving his health. Although unlike many other health stacking champions, I feel like Zac Is the only one that gets more... big i guess.
Ok Cho gath also has scaling size but what i mean is in game it is shown by increasing the range of his E, and that makes sense.
I dont BELEIVE Zacs W and Ults AOE range increase with size. But the main thing i think is Zacs ADs should scale with his health. Chos spikes get bigger. And i feel like Zacs arm going from the size of a needle to a tree-trunk should have an effect.
Now Zac doesnt need this buff, but it is something that i think wont really affect him much, and also would just be a nice interaction.