This is the correct group for your question about zoysia grass for Texas
lawns. You may want to go to the group archives at Google and read what has
already been discussed on the topic of zoysia:

Go to groups.google.com
Click on "Advanced Group Search"
Search for the word "zoysia" in Group "austin.gardening"

Texas A&M is a great source for info on lawns and gardening in Texas:

Go to www.google.com
Click on "Advanced Search"
Search for the word "zoysia" in Domain "tamu.edu"

Check out the Austin Growgreen program:

Go to http://www.ci.austin.tx.us/growgreen

Call the Travis County Extension Service at (512) 854-9600 and ask them to
send you a copy of the "Native and Adapted Plant Guide". It is a nice, slick
version of the guide on the Austin growgreen website. You can ask them
questions, also.

jjhnsn

PS: If the shade is really dense, you may need to use a shade tolerant
ground cover in that area. IMHO a good process for reducing lawn is to
replace problem lawn areas with other alternatives. Makes the yard more
interesting and easier and cheaper to care for.