All Zoltan ships (except ones in sector one on easy mode) carry a Zoltan Shield, which impedes ALL weapons, drones, and teleports. Although uncommon, it's not unheard of to see Zoltan working with Engies in the same ship. In a strange twist of irony, Zoltan prefer to arm their ships with ion and beam weapons, though burst lasers, bombs, and weaker missile launchers can also be commonly spotted. Heavy lasers are rarely seen on Zoltan warships.
Strategy: Beam drones cut through the overshield in a jiffy, and don't miss at the same time. Most beams (even fire or anti-bio beams) hit the shield twice when firing. Once the Zoltan Shield is down, a boarding party will easily get rid of the enemy Zoltan crew members. (provided the medbay/clonebay on the enemy ship is down) Another strategy is to get ion weapons since they do double the effect on the Zoltan Shield. The Ion Blast Mk II alone will take the Zoltan Shield down in 12 seconds provided it does not miss. Ion bombs deal 8 damage to the shield and take it down immediately.
Not counting the ZOLTAN_PEACE (Energy Fighter), the special ship that you encounter at the start of the Zoltan Cruiser unlock series of events (and that later shows up if you choose the correct options).

Energy Fighter / Pirate Fighter
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blueprint: ZOLTAN_FIGHTER, ZOLTAN_FIGHTER_P
Hull Strength: 6-14
Crew: 2-3 Zoltan (Pirate crew is 2-3 random)
Systems
Optional
Medbay (1-3)
Door Control (1-3)
Augmentations
Energy Instigator / Pirate Instigator
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blueprint: ZOLTAN_FIGHTER_DLC, ZOLTAN_FIGHTER_P_DLC
Hull Strength: 6-14
Crew: 2-3 Zoltan (Pirate crew is 2-3 random)
Systems
Optional
Clone Bay (1-3)
Mind Control (1)
Augmentations
Energy Fighter (Peace)
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Unique ship for the Unarmed Zoltan Transport random event. Has no Shields, Weapons, or Zoltan Shield.
blueprint: ZOLTAN_PEACE
Hull Strength: 6-14
Crew: 2-3 Zoltan
Systems
Optional
Medbay (1-3)
Door Control (1-3)

Energy Bomber / Pirate Bomber
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blueprint: ZOLTAN_BOMBER, ZOLTAN_BOMBER_P
Hull Strength: 6-14
Crew: 3-6 Zoltan (Pirate crew is 3-6 random)
Systems
Optional
Drone Control (2-4)
Medbay (1-3)
Door Control (1-3)
Augmentations

Energy Hacker / Pirate Hacker
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blueprint: ZOLTAN_BOMBER_DLC, ZOLTAN_BOMBER_P_DLC Hull Strength: 6-14
Crew: 3-6 Zoltan (Pirate crew is 3-6 random)
Systems
Optional
Clone Bay (1-3)
Door Control (1-3)
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Hacking (1-2)
Augmentations
Weapons
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These Zoltan Ships can have any of the following weapons:
- Basic Laser
- Burst Laser Mark I
- Burst Laser Mark II
- Burst Laser Mark III
- Heavy Laser Mark I
- Heavy Laser Mark II
- Leto Missiles
- Artemis Missiles
- Hermes Missile
- Mini Beam
- Halberd Beam
- Glaive Beam
- Pike Beam
- Fire Beam
- Ion Blast
- Heavy Ion
- Small Bomb
- Ion Bomb
- Hull Beam
Additional weapons with Advanced Edition Content enabled:
Drones
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Zoltan Ships equipped with a Drone Control can have any of the following drones:
Additional drones with Advanced Edition Content enabled: