First write some string which is accepted by this language, i.e.
$L=\{a^{0}, a^{2}, a^{4}, a^{6}....\}$
$L=\{\in,a^{2},a^{4},a^{6},.........\}$
This can be easily be accepted by FSM with $2$ states. So this is not only DCFL but regular too.
Same question we can write in a different way
We can also write $L=\{a^{2n} /n\geq0\}$