[font color="navy" face="Verdana"]A quick search for "mahayana zen" yielded 1.76 million hits , so I'm going to start there, and Wiki's at the top of the page.

the Dharmanet is not a comprehensive site - but, it can get you started. they are eclectic, in a Buddhist sense.
below is a link to their Mahayana page. (not a Mahayana practitioner myself; hope this helps.) Cheers ~

Dharmanet Mahayan page:
http://dharmanet.org/lcmahayanastudy.htm

their Learning Center:
http://dharmanet.org/learning.htm

free downloads on Chan (the Chinese forerunner of Zen) available from Taiwanese Chan Monk - Master Sheng Yen's website:
http://www.shengyen.org/e_content/content/books/books_01.aspx?MType=

Gives good information on the 6 schools of Ch'an(Zen) Buddhism during T'ang dynasty times. Four of the schools are extinct; two are alive in Japan.

I suggested this because of your explicit request for Zen. If you like, I can compile a list for you. I have many on my nook. If you get a chance, google mindfulness bell.

here is a link. Check the directory and learn for yourself.

http://www.mindfulnessbell.org/index.php