Set pagezoom of Safari programmatically
You need to


close Safari
run the Terminal command
re-open Safari


Most (if not all) defaults write commands require you to quit or kill the affected application or process to see the results.



To solve your problem you may think about setting the display resolution from 3840 x 2160 to 1920 x 1080 (Retina / HDPI). This will increase the size of all display elements including text in Safari.

Go to System Preferences &gt; Display and change the resolution there.