I've heard that you can smite Zac's Blobs as if they were minions. So if that is true, does it mean that lantern passive effect can also proc on them? And what about the extra damage to minions mastery? In general are there any special rules for them or do they just count as minions?
I've yet to check the details for these items and masteries (if it only mentions neutral monsters and minions, then it won't proc on "Zacies") but you should know that Smite has always been fully functional on PETS. You can refer to my answer on this question to fully grasp why Zac's blobs count as pets.
TL:DR; Zac's blobs are not minions, they are pet entities and can then be smited. If any items or mastery mentions that it procs on neutral monsters and minions only, then it won't have any effect on pets, and so on Zac's blobs. Smite clearly states (or stated ?) that it works on minions, neutral monsters, and pets (such as Malz's voidlings, Annie's Tibbers, etc).