Live zorin on mbp , canot reboot to Mac again

apologize if i post in the wrong group, I am desperate, i tried zorin 15 live on mbp with ssd 1000GB SAMSUNG and resize the partition(shrinking only partition by 70gb to make room for 2nd one) and reverse it back to original size , when i reboot my mbp will not boot and booting into recovery does not recognize my SSD 1000GB. How can I recover, pls help. Mbp 2012 retina, upgraded SSD 1000 gb Samsung, Catalina os. Many thanks.

Yep, that can be scary. I have done the same thing.
Fortunately, a Boot Repair should help you resolve. What happened is, when you partitioned, then re-partitioned, you lost your boot from the noted position in the partition.
Follow the instructions here with your bootable Zorin 15 media handy;

Please reply to let us know the outcome.

Thanks, did not workout.trying now gpart, doubt its will work on APFS.

Oohh, I see. On a Mac. Hmmm, I have no experience in using a Mac, much less using Ubuntu-derivatives on a Mac computer.
The best I can do then, is try to help your search. Have you seen this thread?

From what I read on the Ubuntu Help Page, the Boot Repair utility should still work on a Mac.
Are you Dual Booting the Zorin OS alongside of MacOS?

No, I tried zorin 15 live on usb,did not install anything on the mac, except I tried to resize the mac one partition to make room for 2nd partition so I shrink it by 70 gb and having 2nd thought ,resize it back to original and did not creating additional partition. when tried to reboot the screen shaw a flashing folder with question mark and did not boot. when log into recovery the volume not recognized. tried boot repair , did not work.

I am starting to understand the issue, now. You did not install Zorin, right? You just started the process, but never completed. You did not resize the partition because you never completed that process.
But now, you cannot boot into the Mac, correct?

Have you tried Mac OS Boot repair?

I used zorin live which run from external usb without installing anything on the computer.
the volume on which my os. x installed, disappear even boot repair dont recognize it. i give up, will format and reinstall and beare the lost of all data which i did not backup.much appreciate your kind attention and intentions .

There is nothing on Zorin Live that could have destroyed your Mac O.S. Boot - since you did not do an installation. The Zorin Live is just a demo. It does not install a boot record nor alter your Boot Record.
If you had done an installation, then it could be possible. But not without it.
I do not say this to absolve Zorin of any liability- I say it because it may indicated Hardware troubles on your Mac.
Before you do any re-installation, I hope you will test your HDD for any errors and do a motherboard test if possible or applicable.
Perhaps this site may also help you in a re-install of your Mac OS without losing data- I hope…

sorry but this is the only way i know how to do this
start up your mac while holding down option
find your mac os drive
most of the time it is called “macintosh HD”
use your mouse or arrows to select the drive then you will boot up mac OS
when your logged into mac os go to settings startup disk
select macintosh hd or what ever drive mac os is on.
now your mac will defaultly boot into mac OS
if you want to get into zorin you need to hold option while your mac is starting
and select your zorin os partition it might be called windows or efi boot
note that after you get into mac os hold option again then boot into mac os coz it wil reset the startup disk to zorin

if you still can not boot into mac OS your os is DESTROYED!
but do not worry
what we need to do is boot into zorin os and install it to your mac
note that we will remove zorin after this
after you installed it download the following program
balena etcher
this is the link

once you done that go to the following website so you can download a mac OS high sierra DMG or iso
i think an iso will be better but please note that it will take a really long time to download
note that we are doing sierra first
we will upgrade it to catalina after
link to download is here

once downloaded install etcher to zorin
after you do this select your dmg or iso then etcher will write it to a usb
once done you can plug in your drive and hold option
once done select your usb drive
after you boot into it FORMAT your drive
this will erase everything on your computer!!!
but it is the only way to get into mac os
install mac os after formating your drive
after done set up your mac
you need to hold option and boot into the os x partition
after done setting up your mac select the startup disk again
and after your mac os will work again
if your on a newer mac i can not find the link
but if this worked just click the tick!