I can't test this at the moment - don't have Zephyr Scale at this time, but here's what I would try:
Export both test cases (TC1) & (TC2) into Excel
Copy & paste the steps from TC1 into TC2
Import the TC2 file and see if it updates the test case
There's a couple of different options depending on what you want to accomplish. You can export to excel and reupload (see MisterB's response).
Or you can clone the test case which will create a new, duplicate test case, then remove or add any new info (descriptions, titles, tags, etc.) on the cloned/duplicate test case.
You can clone multiple test cases at once. There's also an option to bulk edit test cases.
Additionally, Zephyr Scale also has versioning, which allows you to create multiple versions of one test case.
If it's a test case or test steps that get reused often, you may want to check out the call to test feature.