Which is best for cash on delivery in Egypt and the Gulf?

Zid handles it natively. WooCommerce does it with a plugin plus your own order confirmation flow. Shopify does it through an app or a manual payment method.

Can I use the same domain on any of them?

Yes. The domain is independent of the platform, and you point it wherever the store lives. See connecting your domain to Shopify or Zid .

Is WooCommerce cheaper?

Not automatically. You trade platform fees for hosting, maintenance and developer time. Compare the total, and check current pricing yourself rather than trusting a figure in an article.

What if none of the three fits?

Then the answer is a custom store. That is a bigger decision, and our custom e commerce team will tell you honestly when a platform would have been enough.