It is definitely possible that , at the instant when velocity is zero , acceleration is non-zeroFirst of all , you should know that , acceleration is not rate of velocity , but it is rate of change in velocity !Following are 3 cases in which velocity at that instant is zero but acceleration is non-zero :1 – When we apply sudden brakes to the car moving with some initial velocity along positive x axis velocity becomes zero but acceleration is negative and non-zero2 – In vertical upward motion when body is at highest point velocity is zero but acceleration is -g in the absence of air resistance.3 – In SHM of simple pendulum for amplitudes less than 10 degrees , The bob at maximum extreme position has zero velocity , but maximum acceleration because displacement is maximum