Stalker: Call of Pripyat → Pripyat-1 and B28
First, you need to get a suit with a closed breathing system. The most convenient and quickest option is to buy one from the Hawaiian on Yanov. Azot could open the Pripyat-1 overpass, but he refuses to enter the Jupiter plant without security and recommends taking a couple of soldiers with him into the overpass.
Zulu has already joined the squad. He offers to send new fighters to him. The more quests you've completed, the more characters you can take with you. In total, I ended up with a maximum of five: Vano, Vagabond, Lieutenant Sokolov, Zulu, and Azot.
Each stalker will need a suit with a closed breathing system. First, we'll go to Vano, although it doesn't matter who we take first. We need to borrow 5,000 for the suit, then we'll take him to Zulu. Wanderer has no problem with the suit, as he still has the old Monolith suit. But Lieutenant Sokolov doesn't have one, so we'll have to borrow it from Ozersky.
But as always, you won't get anything for free. You need to complete a quest and bring the scientists a sample of the anomalous plant at the edge of the quarry. Once you've brought it, you can go to Zulu. Incidentally, if you've completed all the scientists' quests so far, you'll be awarded the rank of "Discoverer," and once you've brought all three to Zulu, you'll earn another achievement: "Leader."
Once everyone is assembled, Azot opens the door to Jupiter's underground. The most important thing now is to make sure no one on your team dies. This underground passage will be a memorable one. Snorks will attack you all the way to the main hall.
We need to go to the Control Room. As we enter, two snipers appear on opposite sides of the room, and several more Monolith soldiers approach from the direction we came from. We pull the lever and head to the door that opens. We continue down the corridor, shooting jerboas, zombies, and snorks. It's impossible to get lost. We reach a staircase that leads up to a ventilation hatch, and here we are in Pripyat.
After the location loads, watch a short cutscene, after which you appear before Kowalski. The next quest is "Unknown Weapon".
See also:
Call of Pripyat: Quest "Radio Engineering"