Puzzle & Dragons (PAD) developer, GungHo Online Entertainment, has been on a blitz securing a ton of crossovers with various mobile games as a way of celebrating the 4th anniversary of their flagship title. Well, at least that’s the case in Japan. I don’t keep up with the English release other than logging in daily for gold, Magic Stones, and whatever goodies happen to be that day’s reward so I’m not sure how much of a brouhaha the American division is having.
Mobius Final Fantasy is among the many games that’s a part of the collaboration bonanza and the PAD universe has been included into the game by means of the usual special maps and gacha. Both offer unique event-only cards available only until April 30th (Japan Time) or for a set duration. (Event gachas may or may not last the same amount of time as the event itself. Always refer to in-game notices, the official site or Twitter, or the card summon section for exact dates of availability.)

I can’t explain the plot since I didn’t try to read the dialogue but I’ll talk about mechanics of the PAD maps and battling Zeus (not the multiplayer version).

Traversing about the map is nothing special as you’re still fighting sets of battles and moving from one node to the next, but there are added gimmicks such as matching three same-coloured orbs to make them vanish — that’s the most basic match a player can make in Puzzle & Dragons — to reveal more nodes. To make a match, all one has to do is defeat the enemy at a spot with an icon that looks like a blot of coloured ink with eyes. The area will turn into an orb that matches the colour of the two next to it and poof! They’re gone!
The second gimmick is the drop combo. In PAD, drop combos occur when you chain together sets of 3 or more matching orbs in succession. The greater the chain, the bigger the multiplier. High multipliers result in massive damage against foes. Mobius FF offers something similar in that using skills that consume 3 or more element orbs will trigger a combo. If you use 5 or more elements, the drop combo attack will be unleashed against an entire enemy group. There is an exception to this though — Element Drives are excluded from helping the combo build. Don’t worry if you need to use them, attack normally, or utilize skills that use less than 3 orbs because combos won’t break! 😀
A drop combo attack is automatically activated after 3 turns have passed so do your best to stack it since the end result can really turn the tide of the battle. This is especially true against Zeus.

Let me go on a little tangent and share my experience fighting the damnable god.
I mostly play the game on Hard difficulty and went through the entirety of the first map and most of the second map without issue with my Knight of the Round Table and Dancer jobs. When I reached the goal (the area with Zeus waiting) on map 2, I found myself at a stalemate; Wal wouldn’t die and the enemy wouldn’t die either! This went on for probably 3 minutes or maybe more. However, I soon noticed that Zeus was recovering more HP than I was dishing out so I randomly switched to my sub job to see what it was as I’ve forgotten … and promptly died. 😛 (It was a Samurai that wasn’t maxed out.)
The problem with this boss is his ability to recover health and the buff that prevents status ailments to be thrown onto him. Players may notice that it can take a while to wear down his Break Gauge too, and in Full Auto mode, the AI will waste turns hacking and slashing away just to do that.
Unsurprisingly, like previous events, the game wants you to make use of the limited time cards because the key to defeating this foe is to make use of drop combos with PAD-event cards. What makes them special? They come with Expand Skills specifically designed to handle Zeus in some capacity. Some offer defense against his attacks while others grant additional damage. The cards that are dropped by the map mini bosses will gain the skill when they’re evolved to 3-star while cards from the card summon already come with them. For the latter, I’m unsure if they all have such an Expand Skill but you can refer to the Altema Mobius FF wiki for their details.
My KotRT was not equipped with any of them but once I did the gacha draw and got myself a 5-star Sumire, the fight went MUCH faster. And I managed to kill the bastard too. 😛 Equipping more than one PAD card that possesses Zeus Killer (ゼウスキラー) will dramatically up the multiplier damage too.

From experience, I would suggest not using Full Auto when battling this boss so you can focus on building up the drop combo. For what it’s worth, switching the game difficulty back to Normal allowed me to defeat him without the use of a PAD card. ^^
Incidentally, it’s been noted on the Facebook community page that Champ Dusts can undo Zeus’ buff but I’m unsure if it only works in multiplayer. I haven’t noticed the boss using it very much on subsequent replays of the battle so I can’t verify if it works outside of that.