Nesting within ARRAY and IF formula

Building out a holiday request system that is specific to my team and I am struggling to factor in half day holiday requests. I have the following formula:

=ARRAY_CONSTRAIN(ARRAYFORMULA(IF(SUM(($D16>=IF('Vacation request management'!B:B=Workings!$B$2,'Vacation request management'!C:C,""))*(D16<=IF('Vacation request management'!B:B=Workings!$B$2,'Vacation request management'!D:D,"")))>0,"HOL",Workings!$C$2)),1,1)

Essentially I need a way of nesting in that if 'Vacation request management'!F:F="Yes" then populate with "1/2 HOL" but I seem to keep hitting an error. It works perfectly for full day holidays but can't get it to factor in 1/2 days.

I may be being really stupid and it may be really obvious but I've been looking at this for so long I think I have formula blindness.

Any help would be greatly appreciated.