Correct

扎实 vs 实在

/ zhāshi vs shízài /
Strokes

Formula

1
扎扎实实 (AABB)
2
实实在在 (AABB)

Definition

扎实 and 实在 both are Adjectives, which means [steadfast; down-to-earth; real].

Example

扎实 and 实在 both mean "down-to-earth, not impetuous in work or study" and are interchangeable.
1
lùn
无论
gōngzuò
工作
háishi
还是
xué
学习
  
,
dōu
fēicháng
非常
zháshi
扎实
  
(
shízài
实在
  
)
  

Whether study or life, he is devoted.

2
jiàoshòu
教授
de
wénxué
文学
gōng
功底
hěn
zháshi
扎实
  
(
shízài
实在
  
)
  

Professor Li has a good mastery of literature.

扎实 is often reduplicated into 扎扎实实, and 实在 is sometimes reduplicated. They are not interchangeable.
扎扎实实 (AABB) 实实在在 (AABB)
3
xiān
zháshishí
扎扎实实
de
xué
nián
yīng
英语
zài
kāishǐ
开始
gōngzuò
工作
  

You'd better start to work after one-year steady English learning.

4
Yǒu
le
zháshishí
扎扎实实
de
gōngzuò
工作
zuòfēng
作风
  
,
cái
néng
shǐ
使
jiàoxué
教学
yán
科研
shuǐpíng
水平
duàn
不断
gāo
提高
  

Only a down-to-earth way can ensure the constant improvement of your ability in teaching and scientific research.

5
zuò
shénme
什么
shìqing
事情
dōu
shíshízàizài
实实在在
de
  

He works in a down-to-earth way.

扎实 in colloquial language also means "to be at ease"; while 实在 has no such meaning.
6
ér
女儿
zǒu
hòu
zhí
一直
méiyǒu
没有
xiāoxi
消息
  
,
ma
妈妈
xīnli
心里
zǒng
zháshi
扎实
  

The mother couldn't feel at ease after her daughter's leaving.

扎实 also means "sturdy"; while 实在 has no such meaning.
7
Zhè
bāo
xíngli
行李
kǔn
de
hěn
zháshi
扎实
  

The package was packed tightly.