Zoho Books Workflow Customization

My Zoho Books account needs three tightly-integrated pieces of work:

1. Custom quotation workflow
• Build three separate templates (Project, Maintenance Contract, and a generic version) that retain my existing letterhead background.
• Each template must let me switch in and out specific sections so I can adapt the quote content without touching the HTML every time.
• Once saved, the quote should follow my current approval chain and remain fully editable through the Zoho Books UI.

2. Purchase-order workflow
• Create a PO template that mirrors the same letterhead background and visual style as the quotations.
• The PO should be generated directly from an approved quote or manually, while keeping Zoho’s delivery-status tracking intact.

3. Project linkage
• When a quote (or the related PO) is approved, a Project must spin up automatically and inherit the relevant customer, item and billing details so I can begin time-tracking and invoicing immediately.

All configurations must be built inside Zoho Books using its open-source extensions framework, without breaking future updates. Hand over clean code, clear instructions on how to adjust the templates, and a short walkthrough video so I can maintain everything in-house.