I don’t see why it should stop unzipping during launch, but have you tried unzipping the files before with WinRAR? it would mean the system wouldn’t need to do it for you, and saves loading times. Use this page to help reference the symbol meanings inside the zipped file: http://snesorama.us/board/showthread.php?8-What-the-letters-at-the-end-of-ROM-files-mean
I have found no difference effect on using Japanese, US or European ROMs on retropie, but i tend to stick to ROMs that have either nothing after them (best option) or [!] (confirmed good dump or something along those lines).
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