I just wanted to put this somewhere kind of permanent so I wouldn't have to figure it out again. I had to use one of those Internet backup sites to get someone's config from an ESR post from 2008 to finally see how to do this (post, cfg). So, thanks to rep for this.

This allows you to zoom by holding down a key, just like normal zoom except without the annoying/slow lerp effect.

seta cg_fov "98"
seta cg_zoomfov "49"
seta zoom0 "cg_zoomfov 98; +zoom"
seta zoom1 "cg_zoomfov 49; +zoom"
bind shift "+vstr zoom1 zoom0"
seta zoom "+zoom; seta activeAction vstr zoom"
seta activeaction "vstr zoom"
vstr zoom; vstr zoom1; vstr zoom0