There’s no manual yet for zshdb, although there’s help inside the debugger itself.
And since this debugger is a rewrite of the one for bash, you might get some inside looking at the bashdb reference manual.
There are a number of features in bashdb that should be in zshdb. As need arises they will be added. However if you really want that feature, just pull the code from bashdb and move it to zshdb. (Some adjustment due to better modularity may be desired/needed.)
Thanks to Peter Stephenson for the adding necessary support to zsh needed to get this off the ground and make debugging possible.
Thanks to Kate Ward and Stéphane Chazelas for programs used in conjunction with zshdb.