Open Zoho apps in Tabs instead of new browser

Open Zoho apps in Tabs instead of new browser

I am currently testing Zoho and considering a move from Gmail. The only issue I have so far is that when I select "switch too" and choose any other feture it opens a new browser window. My browser (Firefox) is set to open new tabs, but that doesnt seem to matter.

Hoping theres a simple fix or setting.