When dumping a large table in compressed mode, I get a memory limit error or a time limit error.

Compressed dumps are built in memory and because of this are limited to PHP's memory limit. For GZip/BZip2 exports this can be overcome since phpMyAdmin 2.5.4 using $cfg['CompressOnFly'] (enabled by default). Zip exports can not be handled this way, so if you need Zip files for larger dump, you have to use another way.