Recommendation for Balancing Zac
Zac uses HP as his resource, so he has no resource bar. Here's something you could put there:
Give Zac a maximum number of charges of his blobs - the ones that drop when his abilities hit enemies - and put a recharge timer on them. Maybe start with 2-3 max at level 1 and scale up from there. This solves the issue of Zac's infinite sustain in-lane, without slapping mana costs on him.