You can hold the command and plus sign at the same time to zoom.
Unfortunately that doesn't work in TT. I just get a beeping sound. I had the same problem last year and just lived with it. Looks like i will have do it again.
I can see other people had the same problem here https://ttlc.intuit.com/community/taxes/discussion/on-macbook-air-the-p[product key removed]n-won-t-fit-on-my-screen-the-option-of-place-order-is-below-my/00/588807 and it looks like no one was able to fix it then.
One would think Intuit would QA their mac version. -- The internal window (probably some HTML form object) seems to be fixed width. It doesn't expand evenly with the page and doesn't allow for font change, doesn't allow for zoom. It's so bad. I tried external monitors and full screen.