Final Fantasy VII: Crisis Core told the tragic story of Zack Fair, SOLDIER, and mentor to Final Fantasy 7's protagonist, Cloud Strife. Since then, fans have wondered who would win in a straight fight. Both of them are very strong in their own right and have put on stunning displays of strength in their outings. However, they have never really gone mano y mano in the FFVII canon.
Comparing their physical attributes, strengths, weaknesses, and feats in their respective outings should provide a reasonably accurate picture. So, until we get to see the both of them duke it out in remake, here's who would win in a battle of the SOLDIERs.
10 Physical Strength (Zack)
As far as pure physical strength goes, Zack has a sizable advantage over Cloud. He is taller and more muscular, while Cloud is leaner and smaller. He was also a SOLDIER first-class trained by Angeal. Cloud, on the other hand, was just an infantryman till the Nibelheim incident. But after Nibelheim, Cloud's strength was augmented by the Mako. At the peak of his strength, he was able to injure Jenova and Sephiroth with physical strikes alone. Zack succeeded in defeating Genesis and Angeal, but he ultimately lost to Sephiroth. Zack shows superhuman endurance and strength, and he and Cloud are equal in base physical strength.
9 Combat Skills (Cloud)
Zack is an exceptional swordsman. He was trained by Angeal, one of the three most powerful SOLDIER members. He is also proficient in magic use, hand to hand combat, and can use a sniper rifle. Cloud, on the other hand, starts out unfit to even be a SOLDIER. Throughout the game, he develops his unique abilities. Due to the Nibelheim incident, he has also incorporated Zack's moveset into his own. He has also fought and defeated Sephiroth on multiple occasions, something which Zack could not manage.
8 Gear (Cloud)
At his strongest, Cloud uses the Ultima Sword. The sword increases his physical power by a large factor, depending on his health. However, at lower health, the weapon hinders his attacks instead. Aside from that, Cloud has a red ribbon, a gift from Aerith, that protects him from all status ailments. Zack uses the Buster Sword for the entirety of his story and has no notable equipment aside from it. He can also equip the Red Ribbon to protect himself from status ailments. It might be because of the relative brevity of FFVII: Crisis Core, but Zack does not have access to as much equipment as Cloud does, and falls short in this category.
7 Abilities (Tie)
Zack uses several special techniques, partly due to his Limit Break, Digital Mind Wave, that allow him to use and improve on many techniques his allies and enemies use. This includes Sephiroth's Octoslash and Cloud's Meteorain. Both of these are devastating attacks. Cloud's most powerful ability is his Omnislash, a critical 14 hit combo that ends with a powerful downward swing, and creates an explosion. Aside from that, he has several Limit Breaks that allow him to adapt his attacks to different situations. Both of them have many strong abilities resulting in a tie in this category.
6 Magic (Zack)
Zack was trained as a SOLDIER and is proficient in the use of multiple styles of magic. His attacks with materia are not as flashy as those in later games but are strong and effective. He also incorporates his magic use with his fighting style very well, using them to put pressure on his opponents or create space as needed. While Cloud has access to a much wider range of materia, he doesn't use materia as much. Cloud relies a lot on his swordplay and his limit breaks, and careful use of materia would give Zack an advantage here.
5 Summons (Cloud)
While both Zack and Cloud have access to a wide range of summons, including instant death and revive abilities, the sheer number of summoning abilities available to Cloud is much larger. Zack only has a few elemental summonses, while Cloud has several elemental summonses, as well as summons that inflict various status effects, buff himself, or break his opponent's defenses.
While the outcome depends on how well the characters use the summonses, the number of abilities available to Cloud outranks Zack's considerably. Because of the number of options available to him, Cloud takes this one over Zack.
4 Allies (Zack)
Cloud and Zack use their supporting characters in very different ways. For Cloud, his supporting characters are usually with him in every fight. They travel alongside him and are crucial to the combat. A good party composition makes the game a lot easier, and a lot more fun. Every member contributes something very important to the party.
Zack's combat is more focused on Zack himself. His allies aren't physically with him in fights. Instead, they provide him with various advantages using the DMW system. This allows him to draw on the powers of his allies even when he is fighting alone. So, in the event of a one-on-one fight, the advantages that Cloud gets from his party will be completely removed. Zack will still have their abilities, which would give him a sizable advantage over Cloud.
3 Strategies (Cloud)
Both Cloud and Zack are exceptionally well-trained fighters. Their adaptability here is what would make a difference in a fight. While Cloud has had more battles against stronger opponents, he has mostly fought alongside his party. Zack has fought many, many enemies, usually at the same time, by himself. In a one-on-one, that might give him an advantage over Cloud. But the one weakness in Zack's defense is his response to multiple fast strikes. That weakness is what eventually led to his defeat in his fights with Sephiroth. Cloud is an excellent learner in battle and has defeated Sephiroth in every engagement they have had. When it comes to adapting and formulating battle strategies, Cloud has a slight advantage as demonstrated by his victories over Sephiroth.
2 Feats (Zack)
Both of these characters have accomplished a lot in their respective entries. Zack defeated Angeal and Genesis, two of the three strongest Shinra SOLDIERs. Cloud has, however, defeated Sephiroth at every one of their confrontations. Defeating Sephiroth was something that Zack never managed. Both of them have defeated many powerful entities, but Zack has fought and defeated Minerva, who is one of the most powerful entities in the Final Fantasy universe. As far as notable victories or defeats go, Zack takes the edge over Cloud.
1 Conclusion (Cloud)
Both Zack and Cloud are very powerful fighters. A battle between them would be a very close match. However, purely because Cloud gets more time to develop his skills, while Zack dies earlier, Cloud ends up being a little stronger than Zack. In a fight to the death, despite his proficiency in magic and his fantastic durability, Zack would lose out to Cloud. If given a similar time to develop, though, who knows who would win?