Calculate standard deviation and Zscore

Hi all,

 I want to calculate Zscore for each progarm manager by using his score according to his delivery managers project count.Suppose x is the pro.manager and his score is 10 and his delivery manager having projects count 24, then by using score and project count I need to calculate Zscore and for that first need to calculate mean and Standard deviation.

above table is DM table where I have DM and his project count. 

and this table showing pro.manager and his data where I have score and DM name. I have another table i.e PM Name table where I listed only PM names. I set relationship in DM table and PM table using this table.

I have calculated mean using DAX by following formula :

mean= Score / No.of projects

Now I need to calculate Standard deviation and Zscore using above data. Please help me.