Mysql – Optimizing multiple MySQL sub-queries and joins for multiple runs

The query (below) that's running is taking ~0.6 sec which normally would be fine but it gets run almost 1300 times for different custids. How can I make it run faster?

Setup:

Mac OS X 10.7.5
MySQL 5.5.27

Query:

select 
    pn as productId,
    qty,
    invno as invoiceId,
    invdate as invoiceDate
from
    (select 
        trim(pn) as pn,
            qtyord as qty,
            oeinvch.INVNO,
            oeinvch.invdate
    from
        (select 
        invno, invdate
        from
            W_OEINVCH
        where
            (invdate between '2013-08-01' and '2013-11-06') and custid = '13651') as oeinvch
        join W_OEINVCD ON oeinvch.invno = W_OEINVCD.invno) as QtyOrdered

Explain Output:

  *************************** 1. row ***************************
             id: 1
    select_type: PRIMARY
          table: <derived2>
           type: ALL
  possible_keys: NULL
            key: NULL
        key_len: NULL
            ref: NULL
           rows: 38
          Extra:
  *************************** 2. row ***************************
             id: 2
    select_type: DERIVED
          table: <derived3>
           type: ALL
  possible_keys: NULL
            key: NULL
        key_len: NULL
            ref: NULL
           rows: 3
          Extra:
  *************************** 3. row ***************************
             id: 2
    select_type: DERIVED
          table: W_OEINVCD
           type: ALL
  possible_keys: NULL
            key: NULL
        key_len: NULL
            ref: NULL
           rows: 1130159
          Extra: Using where; Using join buffer
  *************************** 4. row ***************************
             id: 3
    select_type: DERIVED
          table: W_OEINVCH
           type: ALL
  possible_keys: NULL
            key: NULL
        key_len: NULL
            ref: NULL
           rows: 102437
          Extra: Using where
  4 rows in set (0.58 sec)

UPDATE FROM EDZE'S ANSWER: 06/11/13

Avoiding derived tables. Execution time is increased now to ~4.2 secs.

Query:

  SELECT 
      TRIM(W_OEINVCD.pn) as productId,
      W_OEINVCD.qtyord as qty,
      W_OEINVCH.invno as invoiceId,
      W_OEINVCH.invdate as invoiceDate
  FROM
      W_OEINVCH
      JOIN W_OEINVCD 
          ON W_OEINVCH.invno = W_OEINVCD.invno
  WHERE
      W_OEINVCH.invdate BETWEEN '2013-08-01' AND '2013-11-06'
      AND W_OEINVCH.custid = '13651'

Explain output:

  *************************** 1. row ***************************
             id: 1
    select_type: SIMPLE
          table: W_OEINVCD
           type: ALL
  possible_keys: NULL
            key: NULL
        key_len: NULL
            ref: NULL
           rows: 1130159
          Extra:
  *************************** 2. row ***************************
             id: 1
    select_type: SIMPLE
          table: W_OEINVCH
           type: ref
  possible_keys: invno
            key: invno
        key_len: 24
            ref: func
           rows: 1
          Extra: Using where
  2 rows in set (0.00 sec)

SHOW CREATE TABLE output:

*************************** 1. row ***************************
       Table: W_OEINVCH
Create Table: CREATE TABLE `W_OEINVCH` (
  `INVNO` char(8) NOT NULL DEFAULT '',
  `INVDATE` date NOT NULL,
  `SHIPDATE` date NOT NULL,
  `OENO` char(8) NOT NULL DEFAULT '',
  `CUSTID` char(8) NOT NULL DEFAULT '',
  KEY `invno` (`INVNO`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)    


*************************** 1. row ***************************
       Table: W_OEINVCD
Create Table: CREATE TABLE `W_OEINVCD` (
  `invno` varchar(45) DEFAULT NULL,
  `pn` varchar(45) DEFAULT NULL,
  `qtyord` int(11) DEFAULT NULL,
  FULLTEXT KEY `invnoIndex` (`invno`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1
1 row in set (0.00 sec)