Yes, you can combine the two cleanses. Add a parasite cleanse, and you have what is called "The Ultimate Cleanse". However, it is much more complicated to do, timing is more critical. If you choose to combine them, be sure to do the SWF (Salt-Water-Flush) BEFORE anything else. It MUST be done on an empty stomach, first thing in the morning.
I started my first Master-Cleanse as an Ultimate Cleanse, but it got too hard to remember the timing between each thing. I ended up dropping the P&B shakes and sticking to the parasite cleanse and MC. Since then, I do them all separately and have better results.
It's up to you what you want to do, in which order, or in which combination. Here's a link to the Ultimate Cleanse info: