How native speakers pronounce “lmn”

with two indices. The amazing relationship between these two symbols is that the product of epsilon ijk with epsilon lmn is equal to the determinant of a three-by-three matrix consisting of Kronecker deltas.

The Remarkable Relationship between the Levi-Civita Symbol and the Kronecker Delta | Deep Dive Maths

you're going to need an identity. Let me  write that down here. If we look at epsilon  ijk times epsilon lmn, we have 6 indices  here. None of them are repeated, so  none of them are what we say  contract. There's no summation  

Kronecker delta and Levi-Civita symbol | Lecture 7 | Vector Calculus for Engineers