@lando242 - Yes that was the first thing I tried by going up to the url and putting in opera://settings/configureCommands. However it wouldn't let me set it to ctrl + z. I figured it out though. The keybinding can still be overridden in the Preferences file, but I just didn't see it at first because everything looks different now.
For those of you who are wondering how to change it, just put opera://about in your url. Then see what location it says your profile is saved to. Go to that folder and open the "preferences" file with some sort of text editor. Find the keybindings section and right after "basic" add ReopenLastClosedTab":["Ctrl+Z"]. So the entire Keybindings section should look exactly like this: {"Keybindings":{"Basic":{"ReopenLastClosedTab":["Ctrl+Z"]}. Now ctrl + z will work to reopen your last tab just like the good 'ole days!
Note of caution: Make a backup of your preferences file first in case you screw it up. Also if Opera auto updates any change could cause serious issues. If you get an update and things are not working just delete your preferences file and Opera will automatically make a new one (and things should work like normal).