C (clang), 170 147 143 143137 bytes

a,j,i;f(m*m,x,z)char*m;{for(;*m;m+=x)for(j=z;j--;puts(""))for(i=-1;++i<x*z;putchar((a-92?a-47?a-45?a-95|j:j-~j-z:i%z-j:~j+z-i%z)?32:a))a=m[i/z];} 

Try it online!Try it online!

• thanks to @ceilingcat suggestion !
• added for loop instead of recursion
• thanks to @Johan du Toit for suggesting using int*array as input!

f(m*m,x,z)char*m;{ function taking:

• m : charchar int array without newlines
• x : width
• z : scale

m+=x;*m&&f(m,x,z); => for(;*m;m+=x)
for every row of input, loop actually better than recursion.

for(j=z;j--;puts(""))
we iterate z times every row of input and put \n each time.

for(i=-1;++i<x*z;putchar(..) )
we put x*z characters.

a=m[i/z]
we use a to save on m[i/z] repetitions which is current input being enlarged.

putchar(( ... )?32:a
... => many nested ternary operators to select proper character based on a and i / j relations which evaluates to 1 or 0 , we then puts a space or a.

C (clang), 170 147 143 bytes

a,j,i;f(m,x,z)char*m;{for(;*m;m+=x)for(j=z;j--;puts(""))for(i=-1;++i<x*z;putchar((a-92?a-47?a-45?a-95|j:j-~j-z:i%z-j:~j+z-i%z)?32:a))a=m[i/z];} 

Try it online!

• thanks to @ceilingcat suggestion !
• added for loop instead of recursion

f(m,x,z)char*m;{ function taking:

• m : char array without newlines
• x : width
• z : scale

m+=x;*m&&f(m,x,z); => for(;*m;m+=x)
for every row of input, loop actually better than recursion.

for(j=z;j--;puts(""))
we iterate z times every row of input and put \n each time.

for(i=-1;++i<x*z;putchar(..) )
we put x*z characters.

a=m[i/z]
we use aa to save on m[i/z] repetitions which is current input being enlarged.

putchar(( ... )?32:a
... => many nested ternary operators to select proper character based on a and i / j relations which evaluates to 1 or 0 , we then puts a space or a

m+=x;*m&&f(m,x,z); => for(;*m;m+=x)
for every row of input was better than recursion.

C (clang), 170 147 143 bytes

a,j,i;f(m,x,z)char*m;{for(;*m;m+=x)for(j=z;j--;puts(""))for(i=-1;++i<x*z;putchar((a-92?a-47?a-45?a-95|j:j-~j-z:i%z-j:~j+z-i%z)?32:a))a=m[i/z];} 

Try it online!

• thanks to @ceilingcat suggestion !
• added for loop instead of recursion

f(m,x,z)char*m;{ function taking:

• m : char array without newlines
• x : width
• z : scale

for(j=z;j--;puts(""))
we iterate z times every row of input and put \n each time

fori=-1;++i<x*z;putchar(i=0;i< x*z;++i)..
we put x*z characters

a=m[i/z]
we use a to save on m[i/z] repetitions which is current input being enlarged

putchar(( ... )?32:a
many ... => many nested ternary operators to select proper character based on a and i / j relations. which evaluates to 1 or 0 , we then puts a space or a

m+=x;*m&&f(m,x,z); => m+=x;*m&&ffor(m,x,z;*m;m+=x);  
finally we go to nextfor every row of input and if it's not \0 we call f() on itwas better than recursion