For the most part, ripping DVDs is perfectly legal as long as it's for you own personal use. The issue, though, is if the DVD uses copy protection that prevents ripping or duplicating. In that case it would not be legal because to do so would involve breaking the copy protection, something that's prohibited by the DMCA (Digital Millennium Copyright Act) here in the US and similar laws elsewhere. There may or may not be a notation on the DVD/packaging itself concerning the copy protection, but you would find out when attempting to rip it...if it's copy-protected the processes will fail using most legal ripping software.

On the technical side, yes, you can transfer ripped DVDs to the Creative Zen Vision M. It supports all of the common formats, including DivX and MPEG, so there shouldn't be a problem. Just note that due to the size of DVDs (~4.7GB) and the player (30GB), you should select a lower quality when ripping the movies for transfer. It won't make a difference when viewing because of the small, lower-quality screen (compared to a full-sized TV), but will save you a lot of space for music and whatnot.

Hope this helps,
John