How do I hide $0 products or coupons on my packing slips?

Add the following code to the top of the Order Header section:

<style>
 .customStyle {}
 .customStyle1 {
   visibility: hidden;
   line-height: 0px;
  }
 </style>

Click the Order Items section.

Replace the opening <tr> tag with the following:

<tr class="customStyle[Extended Price Zero]">

Click Save.

Add the following code above the </style> tag in the Order Header section:

 .adjustment1 {
  display: none;
 } 

Add the following to the <tr> tag you pasted in the Order Items section, after the [Extended Price Zero] field replacement:

adjustment[Adjustment]

Click Save.