Is it possible to make two files with the same size and the same MD5 and CRC32?
Is it possible to make two files with the same size and the same MD5 and CRC32?


It's straight-forward.

First off, we start with Joux's multicollision attack (PDF) to generate $2^{33}$ different same-sized files with the same MD5.  Here's how that works; the MD5 collision attack works by starting with an internal MD5 state $S$, and finding two different blocks $B_0, B_1$ such that, with the MD5 compression function, $\text{MD5Compress}( S, B_0 ) = \text{MD5Compress}( S, B_1 )$.  Finding such a $B_0, B_1$ is fairly easy.

What Joux's attack is ask us to do that 33 times to succesive states; and so we have $2^{33}$ different sequences (as there are $2^{33}$ different ways of selecting $B_0, B_1$ values) that all hash to the same final value.

Once we have that, we know that there exists a pair of files with the same CRC32 value (and actually, we don't need to search through them all, with CRC32, we can find such a pair with linear algebra)