Save Zhijie and Shinra Building or Bust are quests in Chapter 1, "Wutai's Finest", of "Episode INTERmission" in Final Fantasy VII Remake Intergrade. After following Zhijie around the Sector 7 slums, Yuffie Kisaragi and Sonon Kusakabe arrive in the Main Pillar Maintenance Facility, where Zhijie appears to be under threat.
Walkthrough[]
Upon arriving in the Main Pillar Maintenance, the path along the bridge forks: straight ahead is a 
Lightning Materia orb, a bench, and a vending machine, while left progresses forward. Use the bench and upgrade weapons given this opportunity. Lightning materia is very useful to equip for the following battle, and can be paired with 
Elemental Materia to great effect on either Yuffie or Sonon. 
Ramuh Materia should definitely be equipped if possessed. Following the left path leads to a cutscene and then a boss battle.
After the cutscene, a battle commences against the Gigantipede. This is a slow-moving but highly durable enemy, that fires machine guns across its body. It can be deadly when it hits the party with its melee attacks, in the form of its tail or Body Blow attacks. It has no elemental weaknesses, but resists 
Fire, 
Ice, and 
Wind, making 
Lightning the only viable option. At the head, it can be hit with physical attacks, and at the tail, it can be hit with lightning, which fills the stagger gauge faster.
Staying a distance from Gigantipede and using Throw is a viable strategy. When it is pressured (often following its Body Blow attack), this provides a good opportunity to run into its head and attack with melee attacks for greater damage. A number of ATB-consuming abilities, and Lightning Ninjutsu, should also be used before using a fully charged Banishment, to deal immense damage to the boss. Art of War is also effective. Synergizing with Sonon (using 
) grants Synergized Art of War, a more powerful attack consuming both party member's ATB gauges. Though it has nothing to steal, using Yuffie's Mug ability can still be great to get in simple physical damage.
Later in the fight, Gigantipede will use Containment Laser, which is critical to avoid. Further into the fight, it will leave the battlefield and cling to the side of the walls, where it will deploy several Containment Drones, which use lasers to target a party member with missiles. Destroy the drones while dodging their attacks, and await Gigantipede's return with its Death Dive. After this, the tactics are similar to before. When Gigantipede falls to a third of its HP, a cutscene commences as it deploys a drill. Although its melee attacks are slightly stronger, the same strategies as before apply; fully-charged Thunderous Banishments can be used to great effect to defeat the boss.
Sector 7 Clinic taken over by Shinra.
After it is defeated, a cutscene commences, and Yuffie returns to the Sector 7 Slums residential area. If "Chadley's Research", "Mastering Fort Condor", or "The Happy Turtle Ad Campaign" were not complete, this is the last chance to do them. The story is continued by heading to the Sector 7 Undercity Station train. After agreeing with Sonon that Yuffie is ready, a cutscene leads into "Scarlet's Trap" in the next chapter, "Covert Ops".
Hard mode tips[]
Having two 
HP Up Materia (purchased from the nearby vending machine) equipped on each character can be helpful, and pairing elemental with lightning is a good strategy. Yuffie should make use of Brumal Form often to avoid devastating attacks. Otherwise, the typical use of Synergized attacks is the best strategy.
Gigantipede drops two SP books on defeat. After defeating it, before proceeding to the next chapter, it may be best to finish "Mastering Fort Condor", which provides SP in hard mode for each opponent defeated.