Another impressive contribution from Krunoslav Simon was pivotal as his 22 points moved the Croatian club to the same 3-2 record as FMP with just one game left to play in the fight to make the Quarter-Finals.
It was truly stellar first half for Zagreb that left their shocked hosts trailing in their wake. Firstly Andrej Stimac and Luka Zoric combined for 18 points in the opening period to take Zagreb out to a 24-15 lead and it wasn't long before the visitors extended that advantage with a similarly powerful second quarter effort.
Building on that terrific first ten minutes, they locked down FMP and held them to just ten points and were hot both inside and out on offence to lead 44-25 at the break with the free-scoring Simon, Stimac and Zoric all having already racked up double figures.
FMP were stone cold outside for most of the game although when Sasa Stefanovic made an outside play late in the third, it did cut the advantage of Zagreb to single figures at 54-46.
While they worked hard to piece together the wreckage of their first half disaster, overhauling the deficit never looked likely and KK Zagreb held on for a memorable victory.
Filip Covic and Bojan Radetic both claimed 13 points for the home team.
Toni Prostran, KK Zagreb player:
"I am happy we won. We conceded only 63 points and I can say that our defense decided the game. This was a very good team performance."
Vlade Djurovic, FMP coach:
"I am disappointed, I didn't expect such weak game from our side. The first half of the game was our worst half since I took over as coach of FMP. The players told me during the break that they are tired but that shouldn't be an excuse since they are young players. We got better during the second half but we missed too many free throws."
Mladen Jeremic, FMP player:
"Congratulations to Zagreb for their victory. We made the situation even more complicated in the group. We started the game badly, we tried to play better in the second half but we missed too many free throws."