Gul returned figures of 5-65 and was ably supported by Nazir (3-42) after West Indies captain Brian Lara fought a lone battle with a pugnacious 61 here on Saturday.
Pakistan had reached 39-1, with Mohammad Hafeez on 11 and Younis Khan on 10, when bad light ended the day's play with 18.1 overs still to play.
Younis completed 1,000 runs in the calendar year when he reached two. Opener Imran Farhat fell leg-before to Jerome Taylor for nine.
Earlier Gul and Nazir dispelled fears Pakistan would miss their two key strike bowlers Shoaib Akhtar and Mohammad Asif, who were banned after testing positive for banned steroids last week.
Gul took four wickets in his third spell after lunch, including the prize wicket of the world's top batsman, Lara. Gul conceded just 11 runs.
The West Indian captain hit Gul for two boundaries to reach his 48th Test half century, surprisingly his first in five Tests in Pakistan. Gul had his revenge when he produced an unplayable in-swinger which took an edge off Lara's bat for a regulation catch to wicket-keeper Akmal.
Lara, whose previous best of 44 in Pakistan was in his debut Test 16 years ago, hit eight boundaries during his fighting 155-minute knock.
Dwayne Bravo and Dave Mohammed, who batted with Lara, managed 32 and 35 runs respectively.
Gul dismissed the tail in no time for his third five-wicket haul in his 12th Test, also completing 50 wickets in Test cricket.
The first session belonged to the home team who bowled well with Nazir leading the way.
West Indies, who won the toss and elected to bat, were given a confident start before Gul struck by removing opener Daren Ganga for three.
Nazir then took three wickets off 12 deliveries to rock the tourists, trapping Chris Gayle leg-before for 34, Ramnaresh Sarwan (three) caught in the slip and Shivnarine Chanderpaul (five) leg-before to leave West Indies reeling at 52-4.
Gayle hit six boundaries in his rapid 34.
Bravo, who hit a brilliant 108 in his team's tour opener earlier this week, holed out to leg-spinner Danish Kaneria for 32 while Denesh Ramdin (12) miscued a sweep off Kaneria's last ball before lunch to leave West Indies 122-6.