I already have Reserved Instances or Savings Plans that are not going to expire soon. Can Zesty still provide significant savings?

Zesty can still provide savings to you in the interim on any workloads that aren’t covered by the existing commitments. Zesty would then maximize savings once your existing commitments expire.
The scope of these interim savings would depend greatly on the exact nature of your existing commitments as well as your general EC2 footprint. To properly assess what savings could be provided to your business, we can do a POC onboarding for you with nothing more than a read-only IAM role and a few minutes of your time. The POC would also show projections of savings that Zesty can achieve as existing commitments expire.