Zabaleta and Silva get Man City back on track
Victory marked City's first Premier League success on their own turf since beating Bournemouth on September 17, but was only assured in the 86th minute when David Silva claimed a second goal.
After Yaya Toure dispossessed Sebastian Prodl, Silva and Raheem Sterling broke upfield, exchanged passes, and the Spaniard convincingly killed off the game from 15 yards.
Argentine full-back Zabaleta, widely expected to leave when his contract expires at the season's end, scored the opening goal just as a hint of anxiety was beginning to creep into the Etihad Stadium.
For the opening 33 minutes, City had dominated possession without forcing visiting goalkeeper Heurelho Gomes into meaningful action as Watford showed discipline and concentration at the back.
But a Nolito pass found the dangerous De Bruyne in space on the right and, with Adlene Guedioura failing to track Zabaleta, the City defender met his team-mate's cross with a superb half-volley.
Guardiola had sprung a surprise before kick-off by relegating the £50 million ($62.8 million, 59.6 million euros) England defender John Stones to the bench following some recent morale-draining mistakes.
That, and a return to a four-man defence following the use of a back three in the recent losses to Chelsea and Leicester City, gave City a more solid look and Watford rarely, if ever, threatened.
Not that City were wholly convincing at the other end.
De Bruyne's early, probing run ending with a dangerous cross that Jose Holebas cleared well before Sterling's accurate cross found De Bruyne, whose curling shot was well saved.
Aleksandar Kolarov created a chance for Nolito, chipping over from the left wing for the Spaniard to stretch and head over.
- Gundogan injured -
Watford weathered that early pressure, although Prodl earned a yellow card for a hack at Silva.
When De Bruyne managed to pick a hole in the defence with a threaded 22nd-minute pass that the speedy Nolito raced after, Gomes was equal to the task, turning his near-post shot behind.
Finally, Watford's discipline let them down when they gifted the unmarked Zabaleta the chance to claim the opening goal and, before the interval, De Bruyne and Toure would both try their luck with shots.
There was worry for Guardiola when midfielder Ilkay Gundogan was taken off with what looked like a knee injury, being replaced by Fernando just before the interval.
Fernando's first meaningful involvement was to set up De Bruyne for a shot that brought City a corner that could have led two trouble for the visitors.
Gomes allowed the Belgian's low cross to squirm through his grasp, but it was kicked clear by a Watford defender.
Gael Clichy pushed the ball into the area for Nolito, who squeezed neatly between Prodl and Darryl Janmaat before his low shot was blocked by a strong covering challenge from Miguel Britos.
Sterling then picked up possession just inside the Watford half and powered into a central position, a yard inside the area, from where he unleashed a powerful shot that clipped the crossbar.
Zabaleta was cautioned on 74 minutes for a foul on impressive Watford substitute Isaac Success.
From the free-kick, Holebas's far-post cross was met by Etienne Capoue for a shot that Claudio Bravo saved well with his first real action of the evening.
That marked the start of an anxious finale for the hosts as Odion Ighalo sped in to volley Amrabat's excellent cross over the target from eight yards, before Silva settled the home nerves.