Not a chance...
The 2020 uses DDR4, 260-pin memory sticks
The 2013 uses DDR3, 204-pin sticks, so the slots will not accept the newer memory sticks, and won't be recognized by the CPU anyway.
Even if the sticks could work, replacing the RAM on the 21.5-inch iMac is a delicate job, slicing the iMac apart, then removing the logic board (no easy door on the back!), and, there are only two slots for memory on a 21.5-inch iMac.