Now let me start off by saying, this is my strategy, it may not work as well for you depending upon your level, gear, and unlocked heroes, but since I play this mission daily, and have long since the introduction of chapter 12 5 star mastered it (and 5 star mastered all of chapter 12 for that matter) here is my advice and strategy:
Gear:
I am using 3 parts of the Data Set, and the Scroll of Angolob, the parts of the Data Set I use are Combat Analyzer, Reboot, and Encephalizer, the main reason being that in the last wave, a mind controlled Tactical Force is a great asset defensively against Zemo and Hammer.
Steps to be taken
1: Purchase and equip the WWII Captain America alt costume
2: Make sure you have some of the following supplies: Shawarma, Smelling Salts/Neurostim, Hemostatic Spray/Coagulatur, Gene Innoculation (a better alternative to the past mentioned debuff preventers)
3: A strategic Distress Call (check friends profiles and look for a friend using both Warbringer Axe and Coulson's Revenge if available)
The following heroes are also useful:
Union Jack (best choice)
Omega Sentinel (2nd best choice)
Iron Man MK 42 armor alt
Beginning of each wave strategy:
Wave 1:
First chance you get use you distress call, if you found an ally with Coulson's/Warbringer, you will have Coordinated attack and Warbound buffs through the whole fight, if you are using any of the mentioned heroes your strategy varies on who goes first:
Agent with Data Set/SoA: Use the SoA only if Captain America is bleeding, otherwise save it for later, use the Combat Analyzer, if you can determine which villain will go last, use reboot on them, if a villain has already taken a turn, use it on him/her, if 2 villains have taken turns, use it on the one who went 2nd, use Encephalizer and hope Mind Control does it's thing.
Captain America: Attack Moonstone if your in the tactictian suit, then use either Hemostatic Spray, Coagulator, or Gene Innoculation to remove/prevent bleeding on Cap from Boomerang's Razorangs and Grey Gargoyle's Stone Claws, that way Cap is not constantly bleeding out on his counters.
Omega Sentinel: Switch to Tactician class, and use her L9 attack on Moonstone, then the other 2 villains, this way all 3 are disorientated, and may attack one another.
Union Jack: Use his L2 attack on either Grey Gargoyle or Boomerang, this will cause him to pre-emptively attack Grey Gargoyle or Moonstone's melee attacks, he will likely use his Allied Forces passive and gain the pre-emptive counter against ranged attacks following one of CA's shield guard counters anyway.
Iron Man MK 42: Use his L2 attack to cause burning and bleed on Moonstone and Boomerang
Wave 2:
Agent: same stratgy as above, use reboot on Power Armor, if Militant has used Hail Hydra, target him so that the power armor takes the hit from reboot and is ultimately the one under Mind Control
Captain America: Both Bowman and Power Armor can cause stun, if you used Gene Innoculator in round 1, your probably good to go, if not, use Smelling Salts or Neurostim to prevent Cap from being stunned.
Omega Sentinel: Provided Militant has not used Hail Hydra, use her first turn to beef up your team and cause burning on the enemy with her L6 Scrapper attack, this will also trigger her double-strike scrapper ability as Bowman is an Infiltrator, then use her L9 scrapper move to hopefully put down the power armor. If Militant has used Hail Hydra, instead use her L6 Tactician move, followed by her L6 Bruiser move, to build your defense.
Union Jack: If Militant has not used Hail Hydra use Union Jack's L9 attack to put flanked on the Power Armor, if Militant has used Hail Hydra, target Power Armor with Union Jack's L6, Militant will take the hit, and Hail Hydra will be removed.
Iron Man MK 42: If Militant has not used Hail Hydra, use Iron Man's L2, causing burning on all, and bleeding on Militant and Bowman, if Militant has used Hail Hydra, target Power Armor with IM's L9 attack, this will remove Hail Hydra and prevent him from using it again.
Once you have take down all but one of the wave 2 enemies use this as an oppurtunity to restore health and stamina to your team rather then taking the final enemy out, since Bowman only takes a single turn, he is the one who should be left alive during the healing part of the strategy.
Wave 3:
Agent: Regardless of turn order, Tactical Force is the target for Mind Control, since he only takes a single turn he is the lowest threat, but also has the superior defense, this is why your going into this with the data set.
Captain America: Attack Hammer, use Hemostatic Spray or Coagulator if effects from past use of those or Gene Innoculator have worn off, if they have not worn off, use Shield Guard instead
Omega Sentinel: Use her tactician L9 on all 3, first Hammer, of course, then Zemo and Tactical Force
Iron Man MK 42: Open with his L2 as usual
Union Jack: Check to see what counters of his need to be put back in place and use the appropriate attack.
This strategy may sound complex, but over time it becomes 2nd nature.