I have a situation where I need to find receiving antenna impedance when it’s $\lambda/2$ distance from the transmitting antenna. Both are dipole antennas. Is it possible with EZNEC?
I believe that what you want is the effect of mutual coupling of the antennas. That, I believe, can be done in EZNEC by modeling both antennas at the same time (for example the transmitting antenna in the normal way and the receive antenna as a parasitic element not connected to anything).