Rashid Latif said he hoped Pakistan cricket will flourish under the chairman and board.
Miandad held the post of director general of PCB since 2009.
The militant group were responding to a call made by a Pakistan's minister.
After 66 years, 28 chairmen, Pakistan is still wrangling over how to run cricket.
Sethi has been favored by Nawaz Sharif, Ashraf was appointed as board Chairman in 2011.
The pace legend extended his full support to new head coach Moin Khan.
Zaka Ashraf had earlier sacked the former Pakistan captain who was the manager.
Imran Khan lashed out at the country's newly reappointed cricket chief.
Ashraf was reinstated as chairman of the board last month by the Islamabad High Court.
Zaka Ashraf has been sacked as the PCB chief by Pakistan's Prime Minister.