ZNS SSDs shift the responsibility of garbage collection (GC) to the host. However, data migration in GC needs to move data to the host's buffer first and write back to the new location, resulting in an unnecessary end-to-end transfer overhead. Moreover, due to the pre-configured mapping between zones and blocks, GC needs to perform a large number of unnecessary block-to-block data migrations between zones. To address these issues, this paper proposes a simple and efficient data migration method, called IS-AR, with in-storage data migration and address remapping. Based on a full-stack SSD emulator, our evaluation shows that IS-AR reduces GC latency by 6.78× and improves SSD lifetime by 1.17× on average.