Let’s call the dice A, B, C, D.
The probability of A being 1-4 is 4/6=2/3.
The probability of B being 1-4 and not being the same as A is 3/6=1/2.
The probability of C being 1-4 and being neither A or B is 2/6=1/3.
The probability of D being 1-4 and being none of A, B, C is 1/6.
The combined probability is 2/3×1/2×1/3×1/6=1/54.