illegal argument invoked from within "http::collect ...."

You may add HTTP::release in the irules and make the one irule you want to trigger first with priority. You may first test if you add the http::collect in the first priority irule event and http::release in the second priority irule event (also order your irule corectly as per the article).

https://clouddocs.f5.com/api/irules/priority.html

You may also upload the payload from the first irule in a table that the second irule can use but this could be too memory intensive depending on the payload lenght and number of requests:

https://clouddocs.f5.com/api/irules/table.html

https://support.f5.com/csp/article/K13033