For my client, I have created a logic. First created a WorkingHoursTable.

Then created a calculated column with the following formula, in the table which has the start and end dateTime's.
Working Hours Between Dates =
var startDate = [yourStartDateTime].[Date]
var startTime = [yourStartDateTime] - startDate
var endDate = [yourEndDateTime].[Date]
var endTime = [yourEndDateTime] - endDate
var firstFullDay = startDate + 1
var lastFullDay = endDate - 1
var inBetweenWorkingHours =
IF(
firstFullDay > lastFullDay,
0,
SUMX(CALENDAR(firstFullDay, lastFullDay), LOOKUPVALUE(WorkingHoursTable[WorkingHoursInAllDay], WorkingHoursTable[WeekDay], WEEKDAY([Date], 2)))
)
var firstDayStart = LOOKUPVALUE(WorkingHoursTable[StartTime], WorkingHoursTable[WeekDay], WEEKDAY(startDate, 2))
var firstDayEnd = LOOKUPVALUE(WorkingHoursTable[EndTime], WorkingHoursTable[WeekDay], WEEKDAY(startDate, 2))
var lastDayStart = LOOKUPVALUE(WorkingHoursTable[StartTime], WorkingHoursTable[WeekDay], WEEKDAY(endDate, 2))
var lastDayEnd = LOOKUPVALUE(WorkingHoursTable[EndTime], WorkingHoursTable[WeekDay], WEEKDAY(endDate, 2))
var effectiveStartTime = IF(startTime < firstDayStart, firstDayStart, startTime)
var effectiveEndTime = IF(endTime > lastDayEnd, lastDayEnd, endTime)
return
IF(
startDate = endDate,
24 * IF(effectiveEndTime > effectiveStartTime, effectiveEndTime - effectiveStartTime, 0),
var firstDayWorkingHour =
24 *
IF(
startTime > firstDayEnd,
0,
firstDayEnd - effectiveStartTime
)
var lastDayWorkingHour =
24 *
IF(
endTime < lastDayStart,
0,
effectiveEndTime - lastDayStart
)
return firstDayWorkingHour + lastDayWorkingHour + inBetweenWorkingHours
)
In this formula you just set the first 4 variables correctly. Then it will calculate total working hours. Unit will be in hours.
Edit: As I see from your post that your weekends are Friday and Saturday, you will need to use WEEKDAY functions slightly different. You can send 1 as a second parameter to WEEKDAY function, instead of 2. You will also need to modify the WeekDay column of WorkingHoursTable.
After this one, you can parse it to '9d 20H 52m' with your formula.