Show a screenshot of what you mean by "saved my work as a zip file".
If you took the entire project directory and put that into a zip file, then you're safe. Just unzip that and keep working.
If you exported as a .yyz file, then you're also safe. Double-click that .yyz file or select the Import option to restore the project.
If you zipped just the .yyp file, then you just paid a hefty stupid tax. That is the equivalent of saving just the table of contents of a book and recycling the rest.
If you exported as zip file under Create Application, then you're also done for as cgPixel said. That is the final compiled format, not source code, and decompilation is strictly off-limits around here.
In any case, you should have checked that your backup actually contains all the pertinent information, before rashly deleting the original.