Fairfax County (Va.) Retirement System, hired Zak Capital and J.L. Kaplan Associates each to manage $12 million for the $600 million Uniformed Retirement System, said Larry Swartz, executive director of the $2.8 billion system. Zak will invest in midcap growth stocks and Kaplan will invest in small-cap value. Funding is coming from a $24 million small-cap value equity portfolio formerly managed by S.G. Cowen, which was terminated for performance reasons, Mr. Swartz said. Representatives from Cowen did not return phone calls for comment by press time.