Circuit version of a simple if else program
I'm assuming you are using brushed DC motors

Please correct me if I'm wrong but it sounds like you need to reverse each DC motor independently to give you the basic functionality you need so here is a basic DC motor reverse switch: -



Shown is a DPDT (double pole double throw) switch. It has two independent switches that mechanically activate together; one has three contacts in the left column and the other has three contacts on the right column. The centre pin on each switch is the common pin.

This gets you basic motor reverse functionality and if you had this circuit independently on both motors you could operate the two switches and get left, right, up or down.

However, if you want 4 switches to control all four directions from (say) push-buttons you'd have to convert the DPDT switch on each motor to a DPDT relay and have a bit of steering logic using diodes from the 4 push-buttons activating the coils on the two relays.

Assuming that the default un-powered-relay state produces a LEFT direction, powering relay 1 will cause UP motion. From default, powering relay 2 will cause DOWN and powering both relays will cause RIGHT. You may need an on/off contact/relay/switch too.