As of right now, I don't think it's possible. But it shouldn't be too hard to add in by either adding support for odbc_connect or perhaps by passing the CLIENT_ODBC flag to the mysql_connect function if appropriate. The latter would probably be easier, but since I have little knowledge of this either, I don't know how well either solution would work.
Sorry: I, too, do not have experience with ODBC connections. If you wish to attempt this, we can at least answer questions from the Zenphoto point of view. All database handling is isolated to the functions-db script. Probably the only other script that would require change is the setup script in order to provide whatever paremeters the odbc connect might need. These would (presumably) be stored in the zp-config.php file.
One approach to this might be creating an alternate functions-db script. We have done this sort of thing for the authorization library and could follow a similar approach.