https://git.zabbix.com/projects/ZBX/repos/zabbix/browse/templates/net/cisco/cisco_nexus_9000_series_snmp

Currently the template's LLD item for memory is discovering ciscoMemoryPoolTable (1.3.6.1.4.1.9.9.221.1.1.1.1.3). While this is a valid OID, this does not represent the overall memory utilization of the chassis. This represents the memory used by line cards, etc. The overall chassis memory usage is reported under CISCO-PROCESS-MIB (1.3.6.1.4.1.9.9.109.1.1.1.1.2) same as the CPU. We've added the following item prototypes to the CPU LLD and verified the data received back from these items lines up with the data you receive when you run "show system resources" via CLI on the chassis:

Memory free (MB): 1.3.6.1.4.1.9.9.109.1.1.1.1.13.{#SNMPINDEX}
Memory used (MB): 1.3.6.1.4.1.9.9.109.1.1.1.1.12.{#SNMPINDEX}

Tested on Nexus 9000's (C93180YC-FX) running NX-OS 9.3(10), Nexus 9000's (C93240YC-FX2) running NX-OS 10.2(5) as well as Nexus 5000's (N5K-C56128P) running NX-OS 7.3(3).