Bulk Import Test cases using API

Hello there, Team.

We have Zypher Squad installed in our JIRA data centre and are attempting to import the test cases. I see that using the Importer option under the Test tab takes a long time and has a file size limit. Basically, we have a large number of test cases exported from other tools that we want to import into Jira, but the importer is not a preferred method of importing the test cases. As a result, we're looking for APIs that will allow us to import test cases in bulk.