  In this paper, we consider zero range process with an initial condition which
is equivalent to step initial condition in total asymmetric simple exclusion
process (TASEP) as described in a paper by R\'akos, A. and Sch\"utz by using
techniques developed by Borodin, Ferrari, and Sasamoto. The solution for the
transition probability of total asymmetric simple exclusion process for
particles with different hopping rates was first worked out by Sch\"utz and
Rak\"os (2005) for the case when $p=1$ or $q=1$. The formula was later applied
to analyze two speed TASEP (Borodin, Ferrari, and Sasamoto, 2009) with
alternating initial condition. Here we will investigate the two speed TASEP
case with step initial condition.
