[SalesForce] ant deploy error – Maximum size of request reached

I got the same error and tried the code below. It worked. The metadata type is CustomLabel not CustomLabels. It's very strange.

<types>
    <members>*</members>
    <name>CustomLabel</name>
</types>

Reference:
Salesforce Metadata Types

You will be able to pull/push the approval process using a the following package.xml. The ApprovalProcess element will pull down the Approval Process and the Workflow element will pull down any of the actions that are referenced in the Approval Process for that action. Replace CustomObject__c with whatever object(s) your approval processes are on, this will make sure actions such as field updates are also pulled down when doing a refresh.

<?xml version="1.0" encoding="UTF-8"?>
<Package xmlns="http://soap.sforce.com/2006/04/metadata">
    <types>
        <members>*</members>
        <name>ApprovalProcess</name>
    </types>
    <types>
        <members>CustomObject__c</members>
        <name>Workflow</name>
    </types>
    <version>28.0</version>
</Package>

The ability to access approval processes directly without using change sets has only been possible since the Winter '14 release.