Jacob Elevator
Jacob Stage
This is a classic Elevator fight stage. There are no other obstacles to worry about.
Your two best friends in this stage are Zero's spin attack (Mantis), and Zero's slam attack (Gravity).
The spin attack will clear most of the enemies. This includes the elevator moving sections, and the "floors" where the elevator stops. You can damage and destroy the shield enemies before they can set up to block.
If a shield enemy does set up and blocks, the slam attack is the simplest way to destroy them. If they are at close range, you may want to switch back to Sword to have a closer hit box than the Glaive. You can also use Pandamonium's attack to get past the shields if needed.
Jacob Boss - Vile
Vile has the same attacks here as he has for most of the game, with an added Super / Desperation attack. That and you can actually see his life meter.
As with all Vile encounters, he is weak against Ice, but use of Zero's D-Glaive or X's improved half charges are faster (until the last hit).
Desperation Attack
Vile produces 6 equally spaced lightning bolts. They rotate around the screen for several seconds. Occasionally one of the bolts fade out, giving you a space to dash through unharmed. After they stop, they rotate the other way the same amount of time. This isn't particularly hard to dodge, but you cannot hurt Vile during it.
This can also be avoided by flying over the top of the screen with Zero. Release the fly to fall down around the time the rotation switches direction, since it will take about as much time to come down as it does to go up, and you don't want to lose time waiting on Zero to fall.
X's invincibility dash also dodges the lightning, if you happen to have them.