EN
We present here a quite unexpected result: If the product of two quasihomogeneous Toeplitz operators $T_{f}T_{g}$ on the harmonic Bergman space is equal to a Toeplitz operator $T_{h}$, then the product $T_{g}T_{f}$ is also the Toeplitz operator $T_{h}$, and hence $T_{f}$ commutes with $T_{g}$. From this we give necessary and sufficient conditions for the product of two Toeplitz operators, one quasihomogeneous and the other monomial, to be a Toeplitz operator.