ZNS (Zoned Namespaces) SSD is an emerging type of SSD that divides its internal space into zones, which are logical units with a sequential write constraint. By allowing the host to manage these zones directly, it enables more efficient data placement and reduces garbage collection overhead. F2FS (Flash-Friendly File System) is a log-structured file system optimized for NAND flash memory and is one of the default Linux file systems that support ZNS SSDs. Currently, ZNS-based F2FS allocates zones based on file extensions, sizes, and other characteristics. However, it does not support zone allocation policies that consider the level-based lifetime of SST (Static Sorted Table) files, which are the primary data structure of LSM (Log Structured Merge) tree-based key-value stores like RocksDB. Therefore, this paper proposes a technique to reduce the garbage collection overhead of ZNS SSDs by employing a new zone allocation policy that considers the levels of the LSM-tree.