What is the total cost to Accelerate Daring Poro when Undying Loyalty sets its cost to 0 with Rek'Sai in play?

When you determine a cost, you first apply base cost modifiers — Undying Loyalty sets Daring Poro's base cost to 0 — then you look for additional costs such as Accelerate, then apply any increases, then any discounts. Undying Loyalty's cost-setting effect only affects the base cost of the card; it does not reduce or satisfy the separate Accelerate cost granted by Rek'Sai, so you still have to pay the standard Accelerate cost (1 Energy + 1 Power) in full if you want to Accelerate it.