Elements: Items and Weapons can be different Elements. but if you have Elemental DMG% or DMG+ or Elemental Crit on separate items, they need to be the same Element as one or both of your Weapons to be useful.
Example: MH Shock Element with +20% Shock DMG & +5,000 Weapon DMG, OH Poison Element with +5,000 Poison DMG and +15% Toxic, Chest with +5,000 Shock DMG & +30% Elemental Crit (Legend affix).
in this example your MH Weapon Skills DMG are boosted +5k WD (MH), +20% Shock (MH), & +5k Shock (Chest), in that order. the Legend Elemental Crit on the Chest would also give your Shock attacks from your MH a +30% chance to Paralyze enemies.
the OH Weapon Skills DMG are boosted by +5k Poison (OH). also, you would have a +45% chance to cause Toxic Cloud (+15% Toxic on OH & +30% Elemental Crit on Chest).
if all 3 of these items were the same Element, then both weapons would be boosted by everything except for the +5k WD. WD + & % only work on the weapon they are on, but ED +, %, & Elem. Crit. can be on any item and work with any weapon of the same Element.
the first post will help you learn what affixes you can and can’t craft with Crystals, and the second post will help you save time when you find Eternal items and want to craft them.
a number of Legend affixes can only be found on items you get from loot. there are a few Epic affixes that can only go on certain items, like WD affixes on weapons only, Block on OH, Extra Attack Chance on weapons only, MP Reduce on weapons only. Block can be found on a few other Legend Warrior items, and EAC can be found on Will Of the Force Ring & Necklace.
you can save the Zeus if you want or sell it and find one later. you can convert Legend items into Dust so you can buy items out of the Codex later, if you are having a hard time finding an item by killing monsters. Peridot Crystals can be used to level up an item. or you can convert Legend items into Crystals. both require Gold, which is why Farm Builds are so important.