Here's my specially edited zp_zclasses40.sma file. I updated my own for you to use. It is quite different from yours and should work. I'm using it on my server anyway, except mine is a sub-plugin which isnt built into the zombie classes file. Anyway here it is!
NOTE : The regeneration may be more than 250 the first time you run the plugin. It should work properly the second time you run it and onwards. (That happens to my sub-plugin and regeneration zombie)