First of all selection of alphabets are to be done.

3 vowels and 3 consonants can be selected in $^5C_3.^6C_3$ ways

Then they are to be arranged

This can be done in $6!$ ways.

$\therefore$ The required no. of words = $^5C_3.^6C_3.6!$

$=10\times 20\times 720=144000$