I would recommend the following:

• list item Ensure you can choose the correct currency in each language. No one will purchase something in the UK if prices are in New Zealand Dollars.

• list item Detect the country to determine currency and postage options. This way visitors will spend longer on your site, which is an important part of ranking.

• list item Mention the countries you're targeting once on each page. This called be 'free delivery in the UK, New Zealand and Australia' for example.

• list item Write specific blog posts targeting your core keywords plus one of the countries only. This way you have different landing pages for each keyword. Include plenty of links to and images of products in your blog.

• list item Consider creating 3 'Best selling items by country' pages. This way you also have unique landing pages for each country.

• list item Ensure you don't mention currencies or countries by default in your metatags if you're using cookies to change them.

I hope this helps! You can see some additional tips on https://www.indigoextra.com/blog/international-seo.

Google have said that if you have the same site at a different URL then they may apply the same penalty to the new site as they did to the old one, therefore if you wish to redirect a site, I would recommend doing it at the same as you make some other significant changes to it.

I came up with a way of doing this which should work.

On the old domain redirect everything to the home page and then on the home page create a noindex, nofollow page with the following line of code in it:

Where example.com is your NEW domain name.

This way you're using a redirect at the html level, but telling search engines to not index or follow the page.  This should work!