Najib is serving a 12-year prison sentence for graft linked to the multi-billion dollar scandal at state fund 1MDB and faces more bribery charges.
Ahmad Zahid had pleaded not guilty to all charges, and UMNO said he was a victim of political persecution.
Hisyam Teh Poh Teik, a lawyer for Ahmad Zahid, said his team will ask the court for a full acquittal.
The UMNO was voted out for power for the first time in Malaysia's history in 2018 due to widespread anger over corruption allegations against Najib and Ahmad Zahid.
Despite the corruption charges, Anwar appointed Ahmad Zahid to the second-highest office in the country.
Persons:
Ahmad Zahid Hamidi, Anwar Ibrahim's, Anwar, Ahmad Zahid's, Najib Razak, Najib, Ahmad Zahid, General's Chambers, Bernama, Zahid, Hisyam Teh Poh Teik, Rozanna Latiff, Kanupriya Kapoor
Organizations:
Malaysian, Ahmad Zahid's United Malays National Organisation, UMNO, Court, Thomson
Locations:
Kuala Lumpur, Malaysia, KUALA LUMPUR