How to install latest Mailchimp Library without guzzle requirements

So I'm having a really hard time finding out how to install the latest Mailchimp library. I hope someone can help clarify as there seem to be many options and none have worked fro me yet. I read this thread and with interest and reference the solutions suggested in that thread - however I was not able to make any combination of Mailchimp module versions and Mailchimp libraries work together.

I tried using the (latest stable) 4.8 version of the Mailchimp module, got the missing library error, read this info on the module homepage*

So from https://github.com/thinkshout/mailchimp-api-php/releases I downloaded the recommended https://github.com/thinkshout/mailchimp-api-php/releasesFor PHP 5.6 and greater, download v1.0.7-package-no-dev.zip (I'm running PHP 5.6.27 on my server)

That's when I got the missing Guzzle error. Came to this forum. Now I see everyone is looking for answers. I tried downloading earlier versions of the folder as recommended above - v1.0.4 - v1.0.6. But those now cause my site to no longer function and I need to disable the Mailchimp module using drush to get webpage pack.

Then I consider installing Composer - despite the overkill and apparent problems on Drupal 7. But first I read #5 above and try that on my mac however I get errors:

Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - phpunit/phpunit 6.3.0 requires php ^7.0 -> your PHP version (5.5.36) does not satisfy that requirement.
    - phpunit/phpunit 6.2.4 requires php ^7.0 -> your PHP version (5.5.36) does not satisfy that requirement.
    - phpunit/phpunit 6.2.3 requires php ^7.0 -> your PHP version (5.5.36) does not satisfy that requirement.
    - phpunit/phpunit 6.2.2 requires php ^7.0 -> your PHP version (5.5.36) does not satisfy that requirement.
    - Installation request for phpunit/phpunit ^6.2.2 -> satisfiable by phpunit/phpunit[6.2.2, 6.2.3, 6.2.4, 6.3.0].

So then I try installing the last dev version of Mailchimp module - but same problem.

So... a simple Mailchimp library.. how to download it today and with what version of Mailchimp module, stable 4.8 or latest dev - should I pair it?

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*

7.x-4.x

The 7.x-4.x release uses version 3.0 of the MailChimp API. A new library is available here and will need to replace the old library if you are upgrading the module from 7.x-3.x or 7.x2.x.

See the README.txt for library installation instructions.

Readme says:

MailChimp Library Installation
--------------------------------------------------------------------------------

# For MailChimp version 7.x-4.x

To use the Libraries module:

- Install the Libraries module:
https://www.drupal.org/project/libraries

- Download the current release of the MailChimp library:
https://github.com/thinkshout/mailchimp-api-php/files/710410/v1.0.6-pack...

- Locate your libraries directory. Usually:
/sites/all/libraries/

- Extract the archive to:
libraries/mailchimp

- Ensure the directory structure looks like this:

- libraries/
- mailchimp/
- src/
- Mailchimp.php
- MailchimpAPIException.php
- MailchimpCampaigns.php
- MailchimpLists.php
- MailchimpReports.php
- MailchimpTemplates.php
- vendor/
- autoload.php
- composer/
- guzzlehttp/
- psr/
- composer.json
- README.md

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