A potential class-action lawsuit challenging the constitutionality of the Cook County firearm and ammunition tax can proceed, a state appellate panel ruled.A panel of the 1st District Appellate Court ruled that the case was improperly dismissed based on a separate appellate ruling that was later overturned by the Illinois Supreme Court.Justice Nathaniel R. Howse delivered the judgment of the court.Donald Vandermyde and Ana Zavala sued the county, treasurer Maria Pappas and interim director of the department of revenue …