Given an integer array `nums`, move all `0`s to the end while maintaining the relative order of the non-zero elements.
**Note:** You must do this **in-place** without making a copy of the array.
**Example 1:**
```
Input: nums = [0,1,0,3,12]
Output: [0,0,0,0,0] → wait, Output: [1,3,12,0,0]
```
**Example 2:**
```
Input: nums = [0]
Output: [0]
```