i understand that the shaving cannot be for both metzora and nazir tamei (although i have a question about that as well), but i don't remember any reason that the nazir who becomes a metzora and a tamei cannot first shave for tumah and then shave for metzora. this entire sugya assumes that he must first shave for metzora and then for tumah. i believe that if the person can shave first for tumah and then for metzora he can achieve a different result from that set out in the mishna and the braisa.

dmartin, raanana,eretz yisroel