how to cut fields

I want to cut two coloums simulatiously and paste in some other file

for ex:

cut d ' ' -f3 -f4 xxx | paste yyy - > zzz;

from the above i want to cut two fileds 3 and 4 and paste as last coloums of single file (zzz).

how to solve this

regards
rajan

cut -d" " -f3,4 xxx | paste yyy - > zzz