public class PiedDescriptor
{
    public Int64 piece { get; set; }
    public string journal { get; set; }
}

...

string reqSql = "select top 10 piece,journal from PIEDS_V \r\n"
              + "select c_id,c_nom,c_tarif,c_sommeil from CLI where c_tarif<>0 or c_condit<>0 \r\n"
              + "select top 10 piece from pieds_a order by piece desc";

var r = Api.Zselect<PiedDescriptor, (string c_id, string c_nom, Int16 c_tarif, bool c_sommeil), Int64>(Globals.RepData, reqSql);
if (r != null)
{
    List<PiedDescriptor> listPieds = r.List0;
    List<(string c_id, string c_nom, Int16 c_tarif, bool c_sommeil)> listCli = r.List1;
    List<Int64> listPieces = r.List2;
}