What's the best way to start building my shopping, inventory and accounting stack?

What's the best way to start building my shopping, inventory and accounting stack?


I am planning to migrate from another inventory system and online shopping cart. I plan to move to Shopify and use Zoho Inventory and Zoho books for my inventory and accounting purpose. 
However, I don't know whats the best way to start going about it. Is it better to build the Zoho books first, then Zoho inventory then last is Shopify? Or is it better to build Shopify then Zoho books then Zoho inventory? 
I hope you get my point and tell me the best way to build this. I have over 1000s of products and variants