Determining Last Names in excel from a range of full names in varying formats

Ok, I have a column of full names that are in listed in several different formats:

lastName/firstName

lastName, firstName

firstName lastName

firstName middleInitial lastName

firstName middleName lastName

I need to create a formula that extracts lastName from each one of these formats.

I have come up with the following partial formulas:

for determining "/", which works if cell DOES contain "/"

=IF(FIND("/",D2)>0,LEFT(D2,FIND("/",D2)-1),"Rather than displaying this message, if D2 does not contain '/' this results in the dreaded #VALUE!")

for determining ",", which DOES work if cell contains ","

=IF(FIND(",",D2)>0, LEFT(D2, FIND(",",D2)-1),"if D2 does not contain ',' this results in #VALUE! and not this message")

When I attempt to embed these if statements, I only get an error rather than getting a result for "/" or "," types and still do not get anything but errors for an 'else' situation. This was my attempt:

=IF(FIND("/",D5)>0, LEFT(D5,FIND("/",D5)-1), IF(FIND(",",D5), LEFT(D5,(FIND(",",D5))-1), “This should be the close of the first imbedded ‘if’and this statement should populate if D5 does not contain '/' or ',' but instead... #value! ”)

I have additionally googled a solution for pulling lastName if lastName is only one word (it will not work for John St. Paul if I want St. Paul to populate):

IF(RIGHT(D5,LEN(D5)-FIND(" ",SUBSTITUTE(D2," "," ", LEN(D5)-LEN(SUBSTITUTE(D5," ",""))))))

I am not 100% on this, but it spend some more time staring at it I know I could understand what it's saying, but at this time, I can't get my original function to not fail before even getting this far.

So...

If someone has a good idea how to write a single formula that will combine all three of these and if anyone has a good idea about handling the rare times I will have a two-word value for lastName I would be so thankful!

Best,

Andy