Can I setup Zoho Invoice - Zoho CRM integration with Free/Standard edition of Zoho CRM?

If you have Free/Standard edition of Zoho CRM, you can only enable Contacts sync through the integration.

But, if you have a Professional/Enterprise edition, you will be able to sync Products, and have Custom modules enabled in Zoho CRM. You can also enable workflow triggers when you are in Professional/Enterprise editions in Zoho CRM.