Kinda depends on the work. "Split the work" feels like a 50-50 division into two parts (possibly more), while "Split up the work" might fit better if it's impossible to do half-half or if it's more efficient to assign certain tasks completely to one party and other tasks totally to another person or group.
For example, if we're at a restaurant, and we say, "Let's split the bill", that would mean each diner would pay an equal share of the aggregate total. If we say, "Let's split up the bill", then that might mean that one person pays for the food and someone else pays for the drinks.
Either way, it would require some further explanation for all parties to perfectly understand.
Student or Learner