Background UiPath uses Quartz implementation of Cron expressions and is a little limited when compared to cron expressions in Linux. So you can trust this website to give you the extact expressions UiPath Orchestrator supports : Free Online Cron Expression Generator and Describer - FreeFormatter.com
Sadly your query cannot be implemented in a single query. You will need two cron expressions (two dedicated triggers). Here I assume that you will run the bot at 00:00:00 hours / 12:00:00 AM
0 0 0 ? APR,AUG,SEP 6#3 * - At 12:00 AM, on the third Friday of the month, only in April, August, and September
0 0 0 ? JAN,FEB,MAR,MAY,JUN,JUL,OCT,NOV,DEC 6#4 * At 12:00 AM, on the fourth Friday of the month, only in January, February, March, May, June, July, October, November, and December
In UiPath Orchestrator it would look like this:
Hope this helps you and others!