Can someone give me some insight on how to simplify this problem?
Superposition is a good thing to try any time you have multiple sources. In this case, it's mandatory because you have both AC and DC sources. So your overall strategy should be to solve the circuit separately at AC and DC.
If you try drawing the AC and DC equivalent circuits, you'll see what simplifications can be made. Pay careful attention to what happens to the sources in each situation.
EDIT: You can consider each source separately if you'd like. AC or DC equivalent means the circuit with only the AC sources or only the DC sources active. For DC, this means killing \$I_1\$ and \$E_1\$ and replacing the inductor and capacitor with their DC equivalents. For AC, it means killing \$I_2\$ and \$E_2\$. This is useful for looking at the role of inductors and capacitors. For example, the inductor has no effect on the circuit in either case and can be removed.
Remember, your goal is to find the voltage between the two open terminals on the right. With only \$I_1\$ active, you can see that there are only resistors between the two terminals:



simulate this circuit &ndash; Schematic created using CircuitLab
Kirchhoff's Current Law says that none of \$I_1\$'s current leaves the loop on the left. So \$I_1\$ has no effect on the voltage between the terminals on the right. That voltage is zero. So \$I_1\$ has no effect (it does not contribute to the Thevenin voltage), which means you can remove it.