Tribute 1 Synchro Monster; Special Summon from your hand 1 “/Assault Mode” monster whose name includes the Tributed monster's. (This Special Summon is treated as a Special Summon with “Assault Mode Activate”). During your Main Phase: You can banish this card from your GY; Set 1 “Assault Mode Activate” from your hand or Deck, also it can be activated this turn. You can only use each effect of “Assault Mode Zero” once per turn.
Requires lots of setup including adding the /Assault Mode monster to your hand.
/Assault Mode monsters, when destroyed, are able to revive their Synchro counterparts. Assault Mode Zero being able to search and immediately activate Assault Mode Activate lets you go into another /Assault Mode with the newly revived Synchro.
/Assault Mode monsters
Here are the monsters you can use Assault Mode Zero on to summon their /Assault Mode counterparts.
Psi-Reflector allows you to search Assault Mode Activate or cards that mention it in their effect. So depending on whether your /Assault Mode monster is in your hand or deck, search Assault Mode Zero or Assault Mode Activate respectively.
It's a quick-play, that's the biggest strength of this card. You can attack with the Synchro, then activate this card, summon the /Assault Mode, and then attack again.