Former MP Igors Aleksandrovs was fined €4,810, while Dolārs Kleins and Artūrs Kleins were fined respectively 180 and 150 hours community service, and Guntars Veldre was fined €2,220.
The sentence, if not appealed, will come into force February 9. The prosecutor had asked for harsher penalties.
During the reading of the accusation, Latvian Radio heard about 40 surnames of people whose votes were bought.
The Security Police has initiated seven criminal processes on possible vote buying during the 12th Saeima elections.
A total of 10 persons have so far been named suspects in the cases.
In October, Zaķis quit the Unity party, without however laying down his mandate or leaving the party's parliamentary group.