If 2 fields have same name, web browsers ignore one of them. So you can’t have the name as name="post_content" using contact form 7(or anything else)
You can however make the name as name="post_content[]" which tells the browser that the field is not single & the browser won’t ignore any of them. If you use this technique, you can’t use this(as far as i know) with the contact form 7 plugin. You’ll need to either create the form yourself or use a plugin that supports this.