The Zab Judah of now wouldn't do too well because I think he has major confidence issues. Although he's strong and fast, he wouldn't have the mind to deal with with pac. Zab would probably either go into defensive mode like he did against Mayweather or he would just get KO'd. Zab has a suspect chin.
I like Zab Judah because he has taken all comers. I think he puts up a competitive fight if he flghts smart.
Pac would break him down. Prime Judah had all the tools to be a special fighter. Too bad he lacked the mental.