Make sure that documents do not open in Draft Mode or some other view. If you are using Word for Windows, click File > Options > General and clear the check mark next to "Open e-mail attachments and other uneditable files in reading view." See the screen shot below.
Once you have made this change, most (if not all) documents will open in Print Layout view.
The Zoom can be modified via the Zoom control on the right hand side of the Word window, and the last specified zoom ratio in a Word session will be used the next time you start the program.
If you want something more "advanced," you can try MVP Jay Freedman's add-in which restores the behavior of older versions where you could save the view and zoom with individual documents. Download the SaveViewLocMulti ZIP file from his web site at https://jay-freedman.info/.