Who on earth screws up writing rho with a p? Yes, I know that someone will but they need to write the symbol properly.
Zed and two? RLY? (Crossing your Z is a Germanic thing for me, which is why I do it - I grew up in W Germany). Despite that, you would be in no doubt if I wrote a 2 or Z, because I know how to use a fucking pen and I am able to write.
To be fair, I come from an age where cursive means something!
We are heading into an era where being able to use a pen or pencil will border on arcane skills. Calligraphy isn't hard nor is ensuring you get your message across.
Cross your zeros but leave your Os alone (or dot them if you like - I do sometimes). Cross your zeds if you like. Write Greek letters as they should be - a lower case rho starts from the bottom right and is written in a single stroke - it never looks like a "p".
x (eks) is two curves and not a diagonal cross. Multiplication is . or adjacency of symbols, however it might be x depending on context.
The given advice is don't slash the zero. I disagree. Phi is fatter than tall - its not hard to be precise, which I would hope a mathematician might manage.
In the end can you write or not? If not, use a keyboard. Nothing wrong with that per se ...