I am able to get AEST timezone date time with below approach:

       let queryDate = result.values[1];
                    let queryDateObj = new Date(queryDate);
                    log.audit("queryDateObj",queryDateObj);
                    let ASTTimeZone = format.format({
                        value:queryDateObj,
                        type:format.Type.DATETIME,
                        timezone:format.Timezone.AUSTRALIA_SYDNEY
                    });