Zoom in command:
Go to settings (Shell commands)
Input new shell command (should be compatible with your system, this example is for mac)
open --background "obsidian://adv-uri?commandid=window%3Azoom-in"
(Advanced URI plugin is used as well)
If you want more zoom, then repeat that command in new lines as shown.
Go to events
Check “Obsidian starts”
Now zoom in command is executed always when you startup Obsidian.