Lanzar (Spanish for “to throw, launch”) comes from the Latin lanceare “to pierce with a lance.”
From this root, we can see connections to various English words, including: launch (which is a form of throwing!), lance (it is the stick that they wield to pierce!), and even élan (think of ex-lanceare: to take the energy out of the throw!).
We can see the clear l-n-z to l-n-c (or l-n-ch, in the case of launch) mapping. The -z- and -c- sounds are similar and thus often swap.