Windows Update Killed My Dual Boot

Hello - relatively new to Linux, been running Zorin for several months now flawlessly … until yesterday … I have Zorin on a partition w/Windows 10 and the dualboot option at startup. The other day Windows 10 updated and now the dual boot menu is gone and I go straight to Windows on restarts and after shut downs … is there a way to either: a) Reset the dual boot menu at restart or after shutdown, b) reinstall Zorin without losing the data I have stored in that environment, or b) login to Zorin from Windows (using a command prompt or something like that)?

I’ve tried a couple of things I’ve found online from what seem like similar issues, but without success … I did make it to the boot sequence menu in UEFI, but had no idea what I was looking at (I saw the hard “drives” and Windows, but nothing that looked like Zorin). From what I can tell, though, the partition is still intact. Many thanks for any help one may be able to provide.