Zendesk always popup in new tab from window.open()

CTI in our telephony system, use window.open() to pop-up to zendesk ticket page after agent received a call because Zendesk does not allow iframe to Zendesk.

But even we specified a window name in window.open(), Zendesk would always popup in new tab for each call. So we've got a lot of tab of Zendesk in browser.

Any suggestion to solve this problem?
How CTI can popup to Zendesk in same tab for every calls?

Thank you very much.