There are several problems here:
1. z and y have a different number of elements. If you want to stack them as one column on top of another that's ok. However, if you want to stack them as two rows they need to be the same length (i.e. have the same number of columns).
2. epsilon.c is yet a different length! It isn't the same as the length of f.ck either.
3. When calculationg Z and Y you need an explicit multiply sign between the x and the following bracket.
4. I suspect you need subscripts on Z, x and epsilon.c when calculating Z. Similarly for Y.
5. You calxculate epsilon.cu in each part of the if .. else statement, but don't ever use it.
There are probably other errors, but since it's not totally clear to me exactly what you want (as there is no explanation anywhere) that's about as much as I can help with.