Would he direct the same criticism towards Trump? He was eligble, took advantage of student deferements and a somewhat dubious medical exemption, and as president he sent U.S. troops into combat when it was necessary.
There are a lot of criticisms that can be directed at Biden and his performance concerning Afghanistan. They're all justified. But if Zumwalt is going to criticise him for this then he needs to do the same to other past presidents.
I think any young man at the time would have done whatever he could to get out of going to Vietnam.
Obviously it was easier for the wealthy and connected.