Depending on the treatment of Differential Equations you might want to deep dive into a particular aspect: partial differential equations, numerical methods, etc. Maybe (like me) you just want a proof-heavy treatment of the calculation-centric material you've already covered. Or maybe you want to kick things into high gear and fill the gaps as you see fit.

These thoughts inspire my recommendations:

* Introduction to Partial Differential Equations, by Borthwick (build up your DE knowledge leveraging Linear Algebra and MVC)

* Differential Equations, Dynamical Systems, and an Introduction to Chaos, by Hirch, Smale, Devaney (fill the gaps that your DE course left and play with mathematical modeling)

* Multivariable Calculus, by Shimamoto (rigorous multivariable calculus)

* Multivariate Calculus and Geometry, by Dineen (tensor calculus + differentiable manifolds)