If i have a picosecond laser how would that be expressed in terms of zeptoseconds? in terms of petaseconds?

Picosecond = 10 ^ -12 seconds.
Zeptosecond = 10^ -18 seconsds
Petaseonds  =  10^15  seconds

To express Picoseconds into any of other two, you have to divide  10^-12 by the power index of the one in question

1Picosecond :   10^-12  /  10^-18 =    10^ (-12- 18) =  10^ (-12+18)= 10^6  zeptoseconds

1Picosecond :   10^-12  /  10^15 =    10^ (-12-15) =  10^-27  Petaseconds.

1Picosecond = 10^6  zeptoseconds

1Picosecond = 10^-27  Petaseconds