You can also use a join node followed by a switch node using a JSONata expression for the NAND (or change node if an boolean is required).
e.g
[{"id":"34f859394b66e1e1","type":"inject","z":"d1395164b4eec73e","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"zone1","payload":"true","payloadType":"bool","x":180,"y":1400,"wires":[["4487f4117f1be690"]]},{"id":"4487f4117f1be690","type":"join","z":"d1395164b4eec73e","name":"","mode":"custom","build":"object","property":"payload","propertyType":"msg","key":"topic","joiner":"\\n","joinerType":"str","accumulate":true,"timeout":"","count":"1","reduceRight":false,"reduceExp":"","reduceInit":"","reduceInitType":"","reduceFixup":"","x":410,"y":1480,"wires":[["0f138aed999b59b0","5c88e750c1328b74"]]},{"id":"7699491c2b4841bc","type":"inject","z":"d1395164b4eec73e","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"zone1","payload":"false","payloadType":"bool","x":190,"y":1440,"wires":[["4487f4117f1be690"]]},{"id":"a3166e7879679525","type":"inject","z":"d1395164b4eec73e","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"zone2","payload":"true","payloadType":"bool","x":180,"y":1480,"wires":[["4487f4117f1be690"]]},{"id":"95ef21c5a8c1ad9d","type":"inject","z":"d1395164b4eec73e","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"zone2","payload":"false","payloadType":"bool","x":190,"y":1520,"wires":[["4487f4117f1be690"]]},{"id":"a220f4cfdc095426","type":"inject","z":"d1395164b4eec73e","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"zone3","payload":"true","payloadType":"bool","x":180,"y":1560,"wires":[["4487f4117f1be690"]]},{"id":"c3fb69d4f3bec2e3","type":"inject","z":"d1395164b4eec73e","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"zone3","payload":"false","payloadType":"bool","x":190,"y":1600,"wires":[["4487f4117f1be690"]]},{"id":"0f138aed999b59b0","type":"switch","z":"d1395164b4eec73e","name":"","property":"false in [$$.payload.*]","propertyType":"jsonata","rules":[{"t":"true"},{"t":"else"}],"checkall":"true","repair":false,"outputs":2,"x":530,"y":1480,"wires":[["823bab56dd6ca759"],["50dfaab40ecb65b3"]]},{"id":"5c88e750c1328b74","type":"change","z":"d1395164b4eec73e","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"$not(false in [$$.payload.*])","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":520,"y":1580,"wires":[["8adb971c2a53219a"]]},{"id":"50dfaab40ecb65b3","type":"debug","z":"d1395164b4eec73e","name":"not occupied","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":670,"y":1520,"wires":[]},{"id":"823bab56dd6ca759","type":"debug","z":"d1395164b4eec73e","name":"occupied","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":660,"y":1460,"wires":[]},{"id":"8adb971c2a53219a","type":"debug","z":"d1395164b4eec73e","name":"bool","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":670,"y":1580,"wires":[]}]
You could also use link call nodes to do the check in each flow
e.g
[{"id":"9d1662a5a8db42b8","type":"debug","z":"d1395164b4eec73e","name":"zone1","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":570,"y":1400,"wires":[]},{"id":"34f859394b66e1e1","type":"inject","z":"d1395164b4eec73e","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"zone1","payload":"true","payloadType":"bool","x":180,"y":1380,"wires":[["54056971ed073457"]]},{"id":"7699491c2b4841bc","type":"inject","z":"d1395164b4eec73e","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"zone1","payload":"false","payloadType":"bool","x":190,"y":1420,"wires":[["54056971ed073457"]]},{"id":"95ef21c5a8c1ad9d","type":"inject","z":"d1395164b4eec73e","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"zone2","payload":"false","payloadType":"bool","x":190,"y":1540,"wires":[["bc7a0d9881780919"]]},{"id":"a3166e7879679525","type":"inject","z":"d1395164b4eec73e","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"zone2","payload":"true","payloadType":"bool","x":180,"y":1480,"wires":[["bc7a0d9881780919"]]},{"id":"4487f4117f1be690","type":"join","z":"d1395164b4eec73e","name":"","mode":"custom","build":"object","property":"payload","propertyType":"msg","key":"topic","joiner":"\\n","joinerType":"str","accumulate":true,"timeout":"","count":"1","reduceRight":false,"reduceExp":"","reduceInit":"","reduceInitType":"num","reduceFixup":"","x":350,"y":1600,"wires":[["5c88e750c1328b74"]]},{"id":"5c88e750c1328b74","type":"change","z":"d1395164b4eec73e","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"$not(false in [$$.payload.*])","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":520,"y":1600,"wires":[["d2b31733bde8f579"]]},{"id":"54056971ed073457","type":"link call","z":"d1395164b4eec73e","name":"","links":["bbb1681e9ad67793"],"linkType":"static","timeout":"30","x":410,"y":1400,"wires":[["9d1662a5a8db42b8"]]},{"id":"bc7a0d9881780919","type":"link call","z":"d1395164b4eec73e","name":"","links":["bbb1681e9ad67793"],"linkType":"static","timeout":"30","x":410,"y":1520,"wires":[["303927168087d09b"]]},{"id":"303927168087d09b","type":"debug","z":"d1395164b4eec73e","name":"zone1","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":550,"y":1520,"wires":[]},{"id":"bbb1681e9ad67793","type":"link in","z":"d1395164b4eec73e","name":"zone check","links":[],"x":225,"y":1600,"wires":[["4487f4117f1be690"]]},{"id":"d2b31733bde8f579","type":"link out","z":"d1395164b4eec73e","name":"link out 80","mode":"return","links":[],"x":675,"y":1600,"wires":[]}]