It's a Counter Item.
If you are facing a Split Pusher, rush a Zz'Rot and suddenly he has to make real choices.
Bad clear Champ? Get a Zz'Rot for Passive Clear/Push. Of course, you won't have Offensive Stats to Fight, so good luck getting a Gank... but the trade here is you'll be a little harder to gank.
It also comes at a price, as it can really shove a wave. Some Champs don't want the wave shoved, as it leaves them exposed. So they are forced to choose in pushing passively for the advantages (like punishing a Roam for leaving lane, but then being more exposed to a Jungle Gank and Kill).
It's options, layers of them.
That's why I like it.
Also, it's sleeper OP as an ADC Defensive Item... but dang Maw gives you a crap ton of MR with AD if it's Mages blasting you. The extra Gold from it, with the Resistances and the Siege Potential really add up, and once that Siege has opened things up you can always sell it with less 'wasted gold' since it was granting you Gold to lessen the blow over time.
For fun, we did a Ranked with 5 Zz'Rot and 5 Banner of Command, yep even the ADC. He by-passed Boots for 4 Damage Items and Zz'Rot with Banner, was Ashe and took Teleport. So Lane Phase... not so fun. (Zz'Rot was Item 5 and Banner was Item 6, everyone else literally rushed them Items #1 and #2, except Jungle who Upgraded Machete before going Zz'Rot and Banner).
Once we got our plan down, it got really effective.
"Okay, drop EVERYTHING Top, then we all push Mid."
"Okay, 1-3-1 with everything and push those Super Waves!."
"Okay, 2 Rots and Banners Mid, 3 Rots and Banners Bot, we'll 5 Man Push Top!"
If you work together and really synergize them, it's amazing.
Had a friend who wanted to do 5 Ohmwreckers, but we talked him out of it. Not sure that would work as well. LOL!
