You need to try this one. I can't try it but the way of resolve it you can use from my query
$this->getAdapter()
->select()
->from(array('p' => 'productos'))
->joinLeft(array('trans' => $this->getAdapter()
->select()
->from('transferencias', 'SUM(cantidad)')
->where('upc IN (?)', $this->getAdapter()
->select()
->from('productos', 'upc')
)->where('sucursal = ?', 10)
), 'trans.upc = p.upc')
->where('trans.sucursal_clave_destino = ?', 10)
->query()
->fetchAll();