Maintenance plan with semi-annual and annual tasks

My plant currently has 2 maintenance plans for a piece of equipment. One is a 6 month cycle plan, and the other is an annual plan. Every 6 months, the PM order is due for the 6 month plan. Then 6 months later, both the 6 month order, and the annual order are generated and due. I would like to combine these into a single plan that creates a 6 month order with one task list/operation, and then 6 months after completion of that, I would like the annual order to generate with a separate task list/operation. I want 100% shift to ensure the due date is fully 6 months from completion each time. How can I achieve this?