To complete a successful day for the Russian team at Edinburgh's Royal Commonwealth Pool, Mariia Poliakova then struck gold in the women's one-metre springboard ahead of her compatriot Nadezhda Bazhina.
One of the most eagerly-anticipated duels of the week between world champions Zakharov and Kuznetsov and Britain's Olympic gold medallists Jack Laugher and Chris Mears lived up to its billing in the closest of contests.
Going into the last of the six dives, the British pair held a healthy 15.42 point lead but a fine dive -- four-and-a-half somersaults -- by Zakharov and Kuznetsov, which scored a day's best 94.62, changed the complexion of the competition.
Laugher and Mears, under pressure with their last attempt, executed the same dive poorly by their standards, scoring only 78.66 which gave the experienced Russians, who totalled 431.16, victory by a mere 0.54 points.
"It was exciting until the very last dive and there was a lot of tension," said Zakharov.
"It would have been enough for them to do a 7.5 (average score), but we were fighting until the very end and our last dive, our trump card so to say, did the job.
"We were also a bit lucky to dive before them, so that put pressure on them."
It was a measure of revenge for Zakharov, the 2012 Olympic champion, who had been beaten into silver in the 3m individual event on Thursday by Laugher, who missed out on completing his own golden treble after his individual springboard double.
It ensured back-to-back European titles for 27-year-old Zakharov and 28-year-old Kuznetsov while Germany's former world 10m synchro champion Patrick Hausding and Lars Ruediger took the bronze with 394.77.
Like her male team mates, Poliakova saved her best for last to surge from fourth place to the gold medal spot with her final two dives, both worth 61.10 points, which were the highest-scoring of the entire competition.
The 21-year-old ended with a 285.55 total for her five dives, beating her team mate Bazhina, who had led after three rounds, by 9.55. Italy's Elena Bertocchi took bronze with 271.25.
"It is kind of cool to have a title to carry," said Poliakova, as she celebrated her first major triumph.
On Saturday, she will seek to complete the springboard double in the three-metre event.