It is possible to use El Kang's starting forces to defeat Mertick the Mauler, by using his science stations to cast EMP Shockwave on Mertick to take down his shield. Defensive matrix can also be cast on El Kang to make him survive Mertick's attacks.
Also, Mertick's custom AI script can make him not immediatelly counterattacks units that attack him with enough range, making the range of El Kang's attacks another advantage.
It will probably need additional forces to take down Mertick's base, however.
His name is possibly a reference to Don Quixote.