You would be able to combine this if they have a common field that can correlate them. From the example/screenshot, only common field I can see is _time, so my answer is based on _time, change the field if there are any other common fields.
Update
Actually BSN is the common field, so updating it to BSN
index=security-mijnssp "View rendered = /error.jspx" OR "Er is een fout opgetreden op de JSF pagina" | rex "BSN=(?P<BSN>[^<]+) View" | rex "INFO n.s.m.w.l(?P<INFO>[^<]+)"|rex "ERROR n.s.m.w.l(?P<ERROR>[^<]+)"| table INFO,BSN, ERROR, _time |stats values(*) as * by BSN
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