Diep.io vs Zombs.io
Diep.io
Diep.io is a fun tank-like IO game where players play as pencil-drawn tanks on a piece of white (and sometimes gridded) paper filled with other hostile tanks as well as a variety of obstacles and Polygons. Shooting at Polygons and other players will earn you points to level up your tank to the next tier, unlocking a wide range of upgrades (or "classes" as the game calls them). At frequent intervals, AI-controlled bosses will be spawned allowing players to work somewhat cooperatively to earn a ton of experience points.Many players are calling out Diep.io as being a clone of the previously popular Tank.io (not sure what happened to Tank.io though), but considering that it's currently the last game standing, I guess it's safe to say that new players will never know about Tank.io but will instead be able to enjoy its legacy through Diep.io.
Zombs.io
Zombs.io is in some way a more in-depth version of Moomoo.io. It's basically a strategy game where you build a base as well as defenses, like towers and walls, using the resources you've gathered and once everything's secure, you can then put in your gold stash to start the defending. You'll need to defend your stash from hordes of zombies who will usually attack at night along with other hostile players. You can also build gold mines to generate gold and upgrade your gold stash, which will in turn let you upgrade your towers and walls. You can even spend the cash at the shop to buy better weapons or upgrade your existing ones.Zombs.io may be the more interesting game, as compared to Moomoo.io, namely because it has a zombie- and tower defense-theme. If this is a game for you, be sure to check it out!